I was away for a long weekend, so I'm late to respond to this news article, but according to a Journal Sentinel report, Summerfest's attendence was down this year. Way down. Lowest levels since 1993 down.
The report cites the skittish economy and inopportune weather as likely causes, but doesn't mention what I've heard a lot of people say about this year's festival: The line-up wasn't all that great. That common complaint isn't one I completely agree with (I actually thought the line-up was pretty good by Summerfest standards this year, save for my usual complaint about the lack of hip-hop), but surely a few more exciting additions in next year's schedule wouldn't hurt. Summerfest needs its C.C. Sabbathia.