Comments that aren't

A particularly offensive spamming trick is posting the same comment on a very large number of random blogs, the idea being that you can compliment the blog owner on his blog and include in the message a link to your own blog which will increase his Google rating.
A typical message might be:
Great blog! I have put this among my favourites and will certainly come back often to look at it again. You might like to have a look at mine: www......
This comment spam is easy enough to identify, because such messages will not refer to anything specific in your blog, but deleting them is a chore. There are many websites (e.g. this one) suggesting ways of combatting this nuisance, many of them specific to one bloghoster, but some prophylactic measures are off-putting for genuine commenters or are difficult to apply if you get a very large number of genuine comments.
I use comment moderation, which means that every comment is forwarded to me in an email before it is published, and I can choose to reject it or allow it to appear. This works well for me, and also makes it possible to reject comments which, though genuine, I prefer for one reason or another not to have appearing on my blog.

[One woman with whom for some weeks I had been having an enjoyable exchange of views in our respective blogs or by email suddenly became antagonistic because she had begun to receive spam comments and was convinced, in spite of my denials, that I was responsible. So our relationship ended: sad, really.]