There are a few sites that requires you to claim your own weblog. In order to prove the fact that you are the legitimate owner of the blog in question, they require you to put a specific HTML link back to their web site. These links often will contain a random authorization string (cookie) or simply a link back to your profile on their website.
For example, Technorati allows you to register for your own Technorati profile. After registering, you need to claim your blog by putting a specific URL in your blog. After the next run of spidering, Technorati will add the blog to your profile and finally you will be able to put your photograph next to your entries in Technorati’s search results.
Another example, Blogshares –a fantasy stock exchange for blogs– will automatically make any discovered blogs available for trading. However, the owner of every blog has special privileges with regard to their own blogs. Before the owner can do this, first he/she must claim their blog by putting the ‘Listed in Blogshares’ icon pointing to the blog’s profile in Blogshares. Finally, the owner will be able to do owner specific action, such as issuing more shares and LBO. In addition, the owner will receive an additional 1000 shares of their own blog.
The claiming process is supposed to be doable only by the owner of blog in question. Normally, only the owner of the blog will be able to insert an arbitrary link to the blog’s frontpage or sidebar. However, there are a few cases where visitors of the blog will be able to insert arbitrary links to the front page:
Recent comments in sidebar. Another common practice is putting the list of recent comments in the sidebar. This can be potentially exploited by random visitors in order to put an arbitrary link in the front page, and thus, claiming your own blog.
Of course, not every blog with shoutboxes and/or recent comments are susceptible to this exploit. And not every blog without shoutboxes and/or recent comments are safe from these problem, either.
If you are in doubt, you can try posing as a random visitor and try making arbitrary links in your blog’s frontpage. If you can’t do that, your blog is probably safe.