I'm talking about more modern collaborations, like Jay-Z with Linkin Park, or the newest one that I know of, Weezer and Lil Wayne...

What do you think? Any thoughts?

I think it's the worst idea ever. Weezer sold out big time. Because they have different music tastes, the song's result is compromises over compromises. Idiot "gangster" rappers like Lil Wayne or 50 cent should stay away from good rock bands.