Yeah you can, and obviously so you can put more banners on the page because Google only lets you put 3 banners
I don't think it allows bidvertiser..Well i asked someone and he said that Adsense does not allow bidvertiser.
It's not. It's fine to have both. But the end result will be less quality... less visitors... too many ads. Just my opinion though. Plus bidvertiser pays garbage.
You are allowed to put contextaul ads with Adsense now as long as the ads don't look the same. Obviously you can put more ads on your pages use the both, but when it comes to pay, I would think bidvertiser pays about 10-25% of what Adsense pays, not 100% sure on this figure though so I could be wrong.