Anyone scan for proxies?

Does anyone here scan for there own proxies? If so i was just wondering what ports you scan on and about how many proxies you get per a curtained amount of scanning.

I've once been scanning socks proxies, it lead to about 25,000 tested proxies within 2 days and then the ISP was shut down due to the high number of abuse mails to the uplink provider.
In smaller scale its no real problem, large scaled you can't do it on a legal server.

proxy_go, where did you get the list from? Do you know an IP range that is used for proxys?