I know they can grab .com's, I assume .net and .org just the same. Bodog casino had their .com snagged, they moved to .eu so I assume these are safe. However, I am guessing you don't want to buy it from a US based domain registrar as they could be forced into revealing who owns it and into taking it down. Can anyone recommend a registrar that I'll be reasonably safe from the US government? And for that matter, a hosting company with inexpensive VPS servers that won't cooperate with the feds?
This is what namecoin was made for (at least the domain registration part), for now I think they just do .bit addresses but from what I have read they should be able to handle others but don't quote me on that last part :-D
Namecoins are the way to go.
Although right now theres only a small handful of technically savvy people who use/know what they are, hopefully theyll catch on. (so if your website doesnt target that audience I wouldn't put to much stock in it).
But ultimately it's a dns type pointer that a government can't cease. Although the end user needs to know about the .bit dns entry.