I've had to make a change to the comments feature because I've been getting blog spam. These are comments like, "I saw your blog. Great job. Wouldn't you like to look at my blog?" and then there's a link to a web site or blog. Most of the time they're trying to sell something. These comments have not been sent by a person but by a software program that searches for blogs, then automatically posts the same comment in each blog it finds.
If you'd like to leave a comment you'll will be required to complete a word verification step. A word will appear on the screen and you just have to type it in. This verification prevents automated systems from adding comments to my blog, since it takes a human being to read the word and type it in.