Although web pages and email messages are protected as soon as created, copyright registration is needed before U.S. owners can bring suit. Also, prompt registration provides remedies that make lawsuits affordable. Statutory damages of $150,000 (or more, and attorney fees) for willful infringement can be obtained if published works are registered within three months, or unpublished works are registered before they are infringed.
Registration costs only $30.00, and simple application forms with basic instructions are available from the Copyright Office -- TX still appears to be the best choice. Yet, it would be prohibitively expensive for prolific authors or artists to register individual items other than in the context of existing disputes. Their options much improve when multiple works can be registered as a collection."
This, and the other information at hand, seems to say that there *is* an implied copyright as soon as something is created. An email, a webpage, etc. But that in order to actually sue someone over infringement of that copyright you need to have registered the material. How accurate this site is currently, who knows. Becuase Livejournal is its own site, and your posts are individual, but contained on a single page, I'm not sure how that would be defined. If a blanket notice on your info page means you are notifying everyone (and you'd have to take out a registration on the page, which LJ already has a registration for becuase you're using their interface.. so I'm not sure how that works) or if you'd have to take out a registration for each individual post.
I think the problem with most of the information you find about copyight law on the internet is that it's undated. No really, I know people don't check dates of creation. Here is a list of "myths" about USENET and internet publications in general. Again, this doesn't address the concept of actually SUING someone over it. Becuase the concept of suing someone over a USENET post is pretty fucking ridiculous.
And then... the DMCA. This is a great list of information about the DMCA (Digital Millennium Copyright Act), what it means in internet life, and some of the huge cases that have come out of the DMCA. It's from EFF (Electronic Frontier Foundation). They are, of course, anti-DMCA but I don't think that that impinges on their credibility given their long standing and well reasoned arguments.