Web filters like Websense can scan for and detect a proxy as soon as you try to connect to it. The technology is quite simple and all the web filtering systems now use it. It doesn’t matter what the name of the proxy is, how fresh it is or anything else. The proxy will be detected and blocked. Sometimes on the fly and others a little while later by the administrator.
Say you get a proxy to work for a bit. What do you get for all the work involved in finding one that does? Most of these free proxies are are hacker pots designed to either steal your information or plant bots on your computer. The hacker then has control of your machine and can steal credit cards, attack web sites and send out tons of spam all from your IP address. The recent Facebook and Twitter DDOS attacks that took down their entire networks is a classic example of what people using proxies and getting infected enables.
The few that are not hacker related are loaded with advertisements, as that’s how the owner is making money. The owner of the proxy is probably also watching everything you do so they can take whatever information they can, email addresses and such and sell them for a profit.
In either case the owner has no incentive to provide fast response, high bandwidth or compatibility with advanced web site features. You are being used by the proxy owner and they are delivering very little back to you.
Read more about anonymous and free proxy servers below.
http://www.personalvpn.org/danger_proxy_servers.htm