"Twittering" in Enterprise

One year ago we (3 guys from one of the groups in our department) started “something-like-twitter”. We didn’t have any specific goal, just wanted to try how idea of micro-blogging could survive in work environment with very limited amount of potential participants (something around 30-35 people).
It took almost no time to set simple SharePoint list, and first post has appeared. There was no question “What are you doing?”, there were no “friends” and “followers”. Only available options: post and get notifications (RSS or email alert – both provided by SharePoint). From beginning we decided not to tell anyone, we wanted to create initial content, so new participants (if any) would see something (instead of blank page). Plan: “Let see in 3 weeks” . We posted interesting links, question to each other, notes about current projects, etc. To our surprise it was useful even for 3 people.
Two weeks later we have been discovered through our intranet search – and we’ve got 4^th participant (post content looked interesting to him). At this point we’ve sent email to everyone in department about our “something-like-twitter”. Nobody joined.
Three more weeks later we’ve got 5^th participant. After our email she started to read posts, and at some point started to post herself (“this was so 2 weeks ago... i know of this technology but i thought it was a bit "stalkerish".. TRG Twitter just rolls off the tongue. ”).
And so on, and so on (“so on” still within 30-35 people department).
During one year 17 people posted at least once. However, most of content have been created by 5-7 participants. We’ve got about 900 posts.
What is in content:
-- interesting links and other internet findings (somehow technology related);
-- very few posts about current projects;
-- general notes, opinions, etc.
-- several discussions started there, and have been moved to email or in-person conversations (where you can put longer content );
-- very few “What I’m doing now” info;
-- blog posts announcements;
-- jokes and links to funny stories/photos/videos;

Conclusions:
-- micro-blogging is useful even with very limited amount of potential participants;
-- group of enthusiasts is “mast have” condition;
-- initial content (I prefer “Engaging content”) is extremely important.