i personally do for a couple of reasons
- like uw said its easy to swap out sponsors if one craps out on you
- for more filtering - if they clicked an ad and then decided they didnt like the info on the fpa, links at the bottom to other choices is handy because they are pre qualified. you know they read and click banners so they are more likely to buy
- another page for serps
- you can control the popup rotation. many sponsors dont carry your referral code in the popup roatation and many surfers click a banner then the back button after the first page.
- you can even put a popunder to "free" sponsor sites like cemags which will be there when they close - again they are prequalified and this gives you one more shot at making something off of them
those are my reasons for - the reasons against which have already been stated are also quite valid. now you have to decide which is best for you
hope that helps