There's a buzz around the Interweb that because Sony's logos aren't appearing on a Rock Band E3 invite that it's going to be an exclusive for the Xbox 360.
I just wanted to put everyone's mind at ease.
Apart from the 2,207,000 hits you get on Google if you search for '"Rock Band" +PS3', you can always read the official word at Harmonix' Rock Band website
Q: What systems will this be available on?
A: We are putting this out for Xbox 360 and PS3 for Holiday 2007. We're looking into putting it out on other platforms but we haven't announced anything specific.
Easy really. Damn - people read all sorts of things into a simple launch invite. It's probably that everything is running on Xbox's for the demos and Sony wanted no part in it...