Dear Beth,
I guess that it averages out to "business casual." There are definitely folks here who are dressed more formally, and of course folks in black jeans.
If you come to this evening's meeting of the Berkman Bloggers, you'll see some attendees for yourself. Rebecca MacKinnon and Sam Klein will be offering a blogging/wiki teach-in, and the iLaw attendees are invited to participate. There will also be free pizza!
Warm regards from Deborah