MTV Mashups

I've recently come across these (mostly due to boredom) on YouTube and was wondering if anyone else came across these and what their thoughts were? I think some of them are really good and surprisingly match up quite well (who knew).

Here's one example: MTV Mashup: Britney Spears vs Linkin Park - Toxic Faint

Pretty good, but if it wasn't for Linkin Park I probably wouldn't have liked it. The other mash-up I enjoyed was Jay-Z/Linkin Park. That album was pretty good especially that one song Points of Authority/99 Problems.