I can't vouch for Foxit, but viewing PDFs through Evince is also far more efficient in terms of processor usage, especially since flash seems to like to take up all the cycles it can get.
I say add an extra link or make it a cookie preference, so I can have different settings depending on where I am.
- check the user-agent and only scribd for Windows (since that seems to be the only platform where people still use, and hence complain about, Adobe Acrobat Reader)
- make a greasemonkey script to auto-scribd any PDF (so people who like it can do it everywhere and the rest of us don't have to bother)
pdf or scrib'd depending on the outcome of the poll