Do I own my intellectual property on the web?

I am having a dispute with a website that includes computer game reviews submitted by registered members of the site. I do not work for them. They have threatened me because I have posted my reviews on another website. There are no Terms of Agreement to read and verify when making a new member account. This leads me to believe that they are wrong, since as a member I never agreed to any kind of deal. Furthermore, there are no Official Terms of Agreement anywhere on the site for that matter.

One of the editors posted his own TOA on the message board a couple months ago. This seems unprofessional and it still does not prove that they can control my written work. I became a member long before this post existed, and I never agreed upon it. The editors seem to think that by posting their individual terms on a message board that is frequented by less than 1% of the site (literally) makes their rules law.

There exists no Terms of Agreement or Service to read and sign when making a new account. There exists no reference to the ownership of submitted reviews whatsoever, excluding one post on the message board. The reviews that I wrote are my work and I believe they belong to me, and that I shouldn't be pressured into where I use them.