Facebook has helped keep Ron Paul, for better or worse, a figure in U.S. presidential primaries. It had, I believe , an effect on the mayoral race in Ottawa, Canada. So it seems politically active people are there.
It might be worth getting other anecdotes as regards politics to Facebook and social networking sites in general.
The Facebook profile offers a kind of semiotic square to allow Facebook members to define themselves as some flavour of liberal or conservative, apathetic or Other. I recently joined a Facebook petition to leave the political affiliation option open as with the religious affiliation option in the Facebook profile.
Let's not confine our political definitions to Democrat, Republican and Independent. For one thing, that only applies to politics in the United States. Even Canada, home of inoffensiveness, has four different sitting political parties, with a fifth set to get into the Commons next election.
Many people are apolitical because too many think the only possibility is that 'Lemon' on the right and that 'Lemon' on the left. Opening up the option of other categories will reopen those possibilities.