robzilla - 8:15 pm on Apr 21, 2011 (gmt 0)

And if you are, in fact, also running Adsense ads, I would not recommend doing this even if it were only for your pay-per-sale ads. Visitors might confuse the ads, and you would run the risk of being booted from the Adsense program.

If pay-per-sale is all you've got, I don't see any harm in it.