Such services like the one you linked to are almost exclusively used by script kiddies and hackers to commit fraud or do other nefarious things.
It is for this reason, many VPS hosting companies do no allow you to setup a proxy on your VPS. The way they figure it is that if you were legit, you'd have enough money to get a real server and put in a network at your location. Besides, the problems of being behind a proxy are usually enough to outway any potentially legitimate benefits unless you're using dial-up, which is a dying service in most communities.
As Andrew said these are looked down upon by most reputable providers. Not only for what they usually are used for but also for the fact that they normally eat up the CPU. I have seen nph proxy run 100% processor usage per request. It is ridiculous.