For a long time now I’ve removed the generator meta tag from all WordPress installations I’ve setup. Mentioning WordPress is just honey for the bees. Since I removed the meta tags the amount of spam has decreased remarkably. Posts about WordPress are targeted much sooner and for much longer than other posts.
Starting with WordPress 2.4 the generator information is inserted by the core code, as opposed to the theme. This means that the meta tag will reappear even if you have removed it from your theme. However, this is actually a good change, because now you can disable the tag not only from the HTML pages generated by the theme, but also from all other formats WordPress outputs. The information is created by a couple of functions centrally instead of scattered instances through the code.
I’ve created a plugin to accomplish this: No Generator works with the trunk code from svn, and will work with 2.4 once it is released.