eBay Trademark issue with MSN but not Google

[glenngk]

I've recently created an eBay price comparison site and looking to promote it with PPC advertising. I started with Google and got decent results although I finding the whole Ad Words thing very confusing.

I was looking to test some alternatives to Ad Words and figured I'd give Microsoft's Ad Center a shot. However, they refuse to run any ad with the word "eBay" in it, citing trademark issues.

Is this sort of think common to other PPC services? Is it worth it for me to look at Yahoo/AdBrite/etc. ?