Free anonymous proxy servers cannot be trusted. They do not provide reliable service or a privacy policy, and may be operated with malicious intent. But commercial proxy servers have every incentive to provide a clear privacy policy, reliable service, and have no malicious intent.

Rotating proxy services like ProxyMesh and TOR provide higher anonymity than static IP address proxy servers. When IP addresses rotate periodically, it is harder to track you. Using hundreds of static proxy servers can be less anonymous, and it's harder to configure and use them. Open proxies are even worse because they are slow and unreliable.