I agree that it's hard for hobby sites to take legal action. However, it doesn't cost anything to copyright your own work. Copyright is an implied right which starts on the original date of creation. The copyright (c) notice is usually added to reinforce this.
It's not a good idea to abandon all thought of legal protection. Failing to actively protect your work can be seen as abandoning rights. As you say, lawyers are, of course, expensive and so usually unavailable to hobby sites (and will take every opportunity to screw you - as was seen in this recent UK case in a miners' claim:
http://www.timesonline.co.uk/article...140977,00.html)
The law isn't the only way to protect sites. So it's not a case of deciding between lots of protection or no protection and a degree of reasonable protection is justifiable.