Men vs. Women on Twitter

Hmm. According to new research from Harvard Business, more women (55%) are on Twitter than men (45%).  But, men have more followers, by 15%.  "Men also have more reciprocated relationships, in which two users follow each other. This 'follower split' suggests that women are driven less by followers than men, or have more stringent thresholds for reciprocating relationships."  And, not only are men more likely to follow men, but women are 25% more likely to follow a man.According to the study, this man-following has nothing to do with how much he tweets: men and women tweet at the same rate.  What is up with this?  Possible hypotheses (based on nothing but my intuition):

• The format for Twitter (short bursts of information) is more conducive to the male style of communication, whereas women tend to want to be more verbose and explanatory?
• The subjects women tweet about may not be as diverse as those that men tweet?
• Women tend to tweet about their personal lives, men tend to tweet about business?
• Women have higher "follow" standards because their time is valuable and content is their currency?
• Is there something wrong with Harvard Business's methodology for determining who is male and who is female on Twitter?  ("To get this figure, we cross-referenced users' 'real names' against a database of 40,000 strongly gendered names.")

I would like to hear what others think about this "follower split" on Twitter.  More women are online.  Women have more influence on purchase decisions.  Women are more likely to research before making any decision.  People trust "people like me" for advice.  All of these factors would indicate that women would be following other women in droves on Twitter.  Thoughts?