7 of the 10 most followed people on Twitter are women

"# Name (Screen Name) Followers
1. Lady Gaga (ladygaga) 15,117,972
2. Justin Bieber (justinbieber) 13,868,314
3. Katy Perry (katyperry) 11,511,972
4. Barack Obama (BarackObama) 10,872,247
5. Kim Kardashian (KimKardashian) 10,735,244
6. Britney Spears (britneyspears) 10,662,045
7. Shakira (shakira) 9,802,132
8. Rihanna (rihanna) 9,055,660
9. taylorswift13 (taylorswift13) 8,759,295
10. ashton kutcher (aplusk) 8,028,802"
Source:  Retrieved from Twitaholic, 31st October 2011

50% of tweets with links are generated by just 20,000 twitter users

"We study several longstanding questions in media communications research, in the context of the microblogging service Twitter, regarding the production, flow, and consumption of information. To do so, we exploit a recently introduced feature of Twitter---known as Twitter lists---to distinguish between elite users, by which we mean specifically celebrities, bloggers, and representatives of media outlets and other formal organizations, and ordinary users. Based on this classification, we find a striking concentration of attention on Twitter---roughly 50% of tweets consumed are generated by just 20K elite users---where the media produces the most information, but celebrities are the most followed."
Source:  Shaomei Wu, Cornell University, Jake M. Hofman, Yahoo! Research, Winter A. Mason, Yahoo! Research, Duncan J. Watts, Yahoo! Research, 'Twitter Flow' 28th March 2011
(Includes a link to download the full research report)
Note 1 - Why just just looked at tweets with links (& in fact just tweets with B.t.ly Urls:
From the full pdf:
"In addition to the follower graph, we are interested in the content being shared on Twitter|particularly URLs|and so we examined the corpus of all 5B tweets generated over a 223 day period from July 28, 2009 to March 8, 2010 using data from the Twitter \ rehose," the complete stream of all tweets2. Because our objective is to understand the flow of information, it is useful for us to restrict attention to tweets containing URLs, for two reasons. First, URLs add easily identi able tags to individual tweets, allowing us to observe when a particular piece of content is either retweeted or subsequently reintroduced by another user. And second, because URLs point to online content outside of Twitter, they provide a much richer source of variation than is possible in the typical 140 character tweet. Finally, we note that almost all URLs broadcast on Twitter have been shortened using one of a number of URL shorteners, of which the most popular is http://bit.ly/. From the total of 5B tweets recorded during our observation period, therefore, we focus our attention on the subset of 260M containing bit.ly URLs."

Note 2 - According to the authors of the report, in an email to me in response to my queries, 'attention' is actually defined as being potentially exposed to tweets.  So if I follow @aplusk I am paying attention to his tweets.  It's a bit of a shame that they've used this very low measure of involvement, rather than to look at clicks, re-tweets or replies, in my opinion
So in fact the title should say "50% of the potential impressions generated by tweets with links are generated by just 20,000 users"

US House and Senate election winners generally had more fans than the losers

"With most of Election Night’s races already decided, the Facebook political team took a look at whether Facebook “likes” did help predict the 2010 House and Senate winners.
The Data
 More Fans Equals 74% Winning Percentage in Key House Races
Facebook tracked 98 of the most hotly contested House races, as decided by leading political observers, and 74 percent of the candidates with the most Facebook fans won their races:
· 69 candidates with the most Facebook fans won· 24 candidates with the most Facebook fans lost
· 5 races are still too close to call
More Than 80% of Senate Wins Foreshadowed on Facebook
Just over 82 percent of the 34 Senate races that have been decided were won by the candidate with more Facebook fans:
· 28 candidates with the most Facebook fans won
· 6 candidates with the most Facebook fans lost
· 3 races are still too close to call
House Democrat Incumbents Lost on Facebook Before Losing on Election Day
So far, 46 House Democrat incumbents lost their seats yesterday. More than 78% of those incumbents had fewer Facebook fans than their challengers:
· 36 incumbent House Democrats who lost their seat had fewer fans then their Republican challenger
· 10 incumbent House Democrats who lost their seat had more fans than their Republican challenger"
Source:  Facebook, 3rd November 2011

There were 29 tweets per second discussing the first UK election leadership debate

"Final stats: total tweets: 184,396; average frequency 29.06 tweets per second; total tweeters: 36,483"
Source: Tweet from Tweetminster, 15th April 2010