I just spent a few minutes reading the Wikipedia entry on Bill Ayers, the former (depending on your leaning) domestic terrorist/60's radical activist. As an Oberlin grad, I would like to opine that I know his type. Though I don't think anyone I know has tried to make any bombs.
Here's the part that's germane to the presidential election, pulled out as a series of fact (as best I can tell):
1) Bill Ayers and Barack Obama at one time lived in the same neighborhood in the city of Chicago
2) Both had worked on education reform in the state of Illinois.
3) The two met "at a luncheon meeting about school reform."[footnoted in article]
4) Obama was named to the Chicago Annenberg Challenge Project Board of Directors to oversee the distribution of grants in Chicago [of which Mr. Ayers was also a member].
5) Later in 1995, Ayers hosted "a coffee" for "Mr. Obama's first run for office."[footnoted in article]
6) The two served on the board of a community anti-poverty group, the Woods Fund of Chicago, between 2000 and 2002, during which time the board met twelve times.[footnoted in article]
7) In April 2001, Ayers contributed $200 to Obama's re-election fund to the Illinois State Senate.[footnoted in article]
There's more, but that seems the most pertinent. Serving on a couple of boards myself, I know how tenuous those relationships can be, though it also seems clear that Senator Obama knows Bill Ayers better than I know most of my fellow board members. But who knows? Maybe there are some 60's radicals/domestic terrorists serving on the School for Deacons board right now. Good thing I'm not running for high office.