Some proxies don't work correctly, that is, if you check using findmyipinfo.com and whatismyip.com, they show different locations. So it's not clear what the survey will see.
Also the surveys hosted at surveymyopinion.com check the location differently than the others. Some surveys check the location inside the survey too, beyond the initial page.
And, some browsers don't work correctly too, I've been rejected on Chrome, besides being physically in the country (really) and allowed if I use IE.