This is true under US copyright law, and in those nations with harmonized laws. The site could be hosted somewhere else, which might still give rise to infringement in the US but as no one in Outer Nowhere will care it doesn't really matter.
In addition a US (etc) website might require copyright assignment as part of the terms of service. This is possibly enforceable as a contract because there is clearly consideration on both sides (comment content, publishing service). The law says that consideration must be sufficient but not necessarily equal.
Of course the biggest reason that the terms of service would work is that if someone really wanted to challenge them they would have to take the site owner to court, and who does that over blog comments? Possession is nine tenths of the law :)
Copyright ownership is one thing... I think that means that reproducing the comment elsewhere (in the "Best Disqus Comments EVAR Book of 2009" for example) would require permissin from the commenter.
But while you have rights to the creative work of the comment, I think the UGC site in question (whether it's Digg or Reddit) has the right to remove it or futz with it at will.
If I put a whiteboard outside and you draw a picture on it, it seems pretty ridiculous to think that you have the right to get upset if I erase it or even change it (or allow other people to erase it or change it). Of course, if I copied it, framed it, and sold it in a gallery...
Most services with primarily user-generated content have already covered their bases; check out the reddit ToS ("Rules of Usage," item #3) or digg's ToS (item #6) which dumps all their content under the CC umbrella.
Yes, but I dont think the blogging systems have this since every blogger would have to have his/her own TOS and could not be covered by a blanket wordpress or typepad TOS.
I would like to call for all comment systems to provide a mechanism to clearly indicate to users
what rights they have and what rights they are giving out when they write a comment.
Next to 'Submit' button (small print): "by pressing this you agree with TOS".
TOS: "You grant copyright on your comments to site owner" (or "you own your comments").
