Um, no. I want that spot all to myself! I hate it when people try to steal my evil.
This brings about memories of when a competitor to Fawcette Technical Publication's conference series would copy everything we did (down to the format of the brochure). So, I understand some sensitivity on behalf of conference producers to brands and trademarks.
That said, all this does is give IT@Cork a bunch of free publicity. All Tom has to do is change it to "Future of the Web Workshop" and the lawyers don't have a case and they get all this free publicity.
It looks like O'Reilly is claiming a service mark on "web 2.0 conference" if you visit their conference Web site. IT@Cork's site says "Web 2.0 Half Day Conference." That could, possibly, be confusing to people, so CMP and O'Reilly probably does have a legal case. But, probably not if they change the name to "Web 2.0 Half Day Symposium" or something like that.
Either way, I don't think it's confusing enough to warrant the lawyers and the impending bad PR for CMP and O'Reilly.
Update: O'Reilly responds here.