So I've heard they (co.cc registry) sometimes take away domains that get good traffic (even if you donate to them) Is it true?...
True or not, it's a free sub-domain for you to use. I'm sure they can take it away from you anytime they want.
Good point. I think I might actually drop my co.ccs and the rest of free subdomains (co.tv, cz.cc, cx.cc, ce.ms, cw.cm) I bought 5 x .us today (only $3.49 with "cjcUS349" coupon) While I use free "domains" mostly for a minisites on free webhosting but still, if I buil d links to them I rather be sure they will be mine for as long as I want.
Actually if your domain get good traffic and you have earnings from that domain you should upgrade it to commercial instead of donating them to avoid take away.to know more about renewal see here http://www.webmarketingboard.com/Thread-co-cc-domain-upgarading-and-renewal-issues
I suppose that you are aware that it is free domain name is easy to get but at the same time that is easy to lose as well.