I wanted to illustrate the idea of community retrieval with a task, so I decided that on Sunday 6 January I would call every single person in my mobile phone. The outcome is below. (I've used initials instead of people's names.)

11:25am Aardvark - This isn't a real person, it's there so I don't call someone from my pocket by mistake.
AE - A friend of my father's. No answer, which is good because I'd have nothing to say to her.
ABS Roofing - Closed for business. Didn't leave a message.
A? - Ugh. How embarrassing. I don't know this guy at all - he's the neighbour of our rental property in Birmingham. I pretended like I was checking whether the tenants were causing him any trouble. He thought I was some crazy stalker or something.
Adrian Gregg Guttering - Quite handy, reminded him that we need some work done.
AP - A work friend. At last, a normal conversation!
AS - A Uni friend. Lovely to catch up. We chatted about the <a href="http://sf0.org/getareaction/">road trip</a>.
BREAK. So soon, you ask? This is surprisingly exhausting!
1:20pm AM - Uni friend, haven't spoken to him in ages. A nice, brief but satisfying conversation.
AC - My boss. Actually my boss's boss. I almost wimped out of calling her, but I couldn't skimp on <em>tasking...</em> Eventually, I formed a plan in my head of what I would say to her... but her phone was turned off. Phew.
A? - Ex-fiancee of a Uni friend. She didn't answer, but I left her a message asking how she's been doing since they broke up. Felt good.
AL - Overworked programmer. At this point I decided that, for the sake of preventing rudeness and embarrasment, I would exclude work people for the rest of the task.
AR - Old friend. Left him a message.
AS - My flatmate (and brother-in-law). He was in the next room. The conversation went like this. Him: "What are you doing?" Me: "Calling everyone I know." Him: "Want to go to the pub later?" Me: "Yes. Yes I do."
AB - A film producer in Sweden. I left a message asking how her adaptation of my story was coming along. It occurs to me that I can't remember if she paid me.
AS - A long dead number for my cousin. Deleted it.
AW1 - A friend in Germany that I haven't spoken to in ages. I was hesitant about calling her, but we ended up chatting for about forty minutes. My bill is going to be huuuuge. I was tempted to take another break after this, but I hadn't even done "A" yet!
AW2 - A friend of my mum's, but I quite enjoyed chatting to her.
AW3 - A Uni friend, but the number didn't work. Must get his new number.
Anthola Insurance - Closed for business. Left no message.
ARC Alarms - Actually <em>not</em> closed for business. I really like these guys. Still, I claimed I had dialled a wrong number. Not really the point of the task, but hey...
2:41pm Barclays - A machine.
Barclays2 - Ditto.
BM - Talked to her about the road trip. She might come. Excellent!
BK, BM and BV - Three friends I met through a work friend. I invited them all to the pub (two in person, one on voicemail). None of them came, as it turned out.
Bulk Waste - A machine.
Burford Printing - Why on earth do I have this number in my phone? Closed for business. Deleted.
Burglar Alarm - The same number as ARC Alarms, who I'd already called. Deleted.
2:47pm Cameron from SF0! - It'd be a bit early in the morning US time. I'll come back to this one.
C&E - Family friends in America. Wished them a Happy New Year and chatted a while.
CS - Me. Busy.
C&G - My uncle and aunt. They've just moved house though, so I have the wrong number. Must get the new one.
Citizen's Advice - A machine.
CB - I felt a bit awkward calling up this neglected Uni friend. I wished her a Happy New Year, but it was a bit stilted.
CY - My dad's cousin. She instanty hung up and called me back, and we chatted for about 20 mins. Lovely!
Cleaners - House cleaners in Birmingham. I asked "Do you clean fish tanks?" "No sir, sorry sir." "Do you know anywhere that cleans fishtanks?" "No sir, sorry sir." I've never been called sir so often on such a short space of time. I think she was Polish. Or Russian.
Curry Eastern Empire - I asked for opening hours. I might take my wife there next week as a treat. (It's a very posh curry restaurant!)
3:16pm Dad - Someone I was glad to call.
DM - It took me a while to remember who this was. I called him to wish him a Happy New Year. I don't think he remembered who I was, but he was very polite and wished me one too.
DJ - Yay! An old friend's wife who's pregnant with her first - and I hadn't spoken to her for months. I teased her that she conceived at my wedding.
DS - My little bro. He's based in US, so still too early to call him.
Dentist Brixton - Closed.
DialABike - Closed. Left a silly message along the lines of "My bike is snoring badly, can you fix it?"
DS - Mother-in-law. Very pleasant conversation.
DE - Mum's boyfriend. He was busy working in his shop, so he couldn't talk.
Doctor Brixton - Machine.
Doctor Balham - An old number. I left another prank message and deleted the number. "Doctor, doctor, I keep thinking I'm a curtain." - "Pull yourself together, man!
3:23pm E&A - NO WAY am I calling these people. Tasking or no. Deleted.
Electric - I told our electrician that we wouldn't be using him again because he overcharged us. Most satisfying - I wouldn't have done that had this task not encouraged me to call him.
E? - I have no idea who this person is. I called her and asked her how we knew each other. She didn't know either. <small>Not deleted though!</small>
EC - Tenant who is not paying her rent. No answer. Surprise surprise.
Endsleigh - Machine.
ES - Dutch friend. Left him a message about the road trip.
ES - My sis. Chatted aimlessly for a few minutes.
Estate - Haart - I froze up when they answered this one. Then I came up with a lame query - something like "Do you have anything for sale in the £10-£20 price range?" Embarrassed.
3:26pm FE - Uni friend. No answer.
Family F - Friends that I usually MSN with, never call. Wheee! What a fun conversation!
3:47pm GH - No idea who this is. No answer.
G - Uni friend that I've sadly fallen out of touch with. Number didn't wprk.
GS - Uni friend. Wished her a Happy New Year, and made all kinds of false promises that we should meet up soon. D'oh...
GC - Friend. Would have loved to catch up with this guy, but no answer.
GP - Friend. Had a mildly awkward conversation.
GS - My cousin. Never answers his phone.
BREAK. I suddenly felt quite exhausted and went to the pub. A couple of hours and a couple of drinks later I realised that it was quite unlikely that I would get through every person in my phone, and to be honest I didn't really feel like it. It's surprisingly draining. So I just skipped forward and called (most of) my favourite people, spending about another hour on the phone in total before calling it a night. JM, JQ, JH, KT, KJ (no answer), LW, MW (no answer), MD, RM, RW.

The conclusion is that mobile phones not only retrieve communities, but enlarge them, to the point where they can become unmanageable.