Marshall - 4:58 pm on Feb 25, 2012 (gmt 0)
This is not legal advice, just personal advice.
If your work is important enough to you, it is well worth the registration fee for a copyright ($30 online, $50 the old fashion way. See Registering a Work [copyright.gov]), especially since it is so much easier to steal work these days. There are very few lawyers I know of (and I know plenty) who will take a copyright case without it.