Blogger doesn't use trackback (the ability to automatically receive notice when other posts link to your blog post) which is a shame (though Blogger does have linkback). However the trackback system has been largely broken by immoral people who have resorted to sending false trackbacks. Just like the email scammers that have caused huge amounts of grief for those that attempt to use email these trackback spammers burden others with their intrusive acts. It is a shame people insist on being so immoral but just as always there are plenty of people who insist on acting immorally and technology often makes it easier for these people to burden more people with their immoral behavior than they could impose their bad behavior on without technology.
For wordpress bloggers Akismet does a great job of filtering out spam (comments, pingbacks and trackbacks). But our blogs are now getting thousands of false trackbacks per day and I don't appreciate the huge amount of spam (which makes it impossible to check and see if any false positives were found). Many site have given up and just eliminated trackback (sort of like giving up on the auto because people put big advertising signs in the street so that no one could actual use the roads for the intended purpose and we just let these people remove the rights of others to travel).
I tried a plugin from Rice University: Trackback Validator Plugin and then WordPress 2.0 / 1.5.x Plugin: Referrer Bouncer, they didn't do enough good that I could tell (I only tried for an hour but if they did anything they just reduced the spam some).
In reading the comments on those trying the above I read about an akismet option to automatically delete any spam that is on post older than one month old. This seems to be working very well, for now, and I believe it allows posts to accept legitimate trackbacks which I think is important. Another success for open source software solutions - yay.