Fighting spam is a pain in the ass for all of us, but don't let it stop you from blogging. I recently had a similar problem with a massive increase in email spam - but some preventative measures - http://blog.aplpi.com/index.php/2008/04/22/backscatter-and-joe-jobs/ seem to have mostly gotten things back on track. I'm sure you'll come up with a similar solution for your blog (and I look forward to reading about it, we don't get enough traffic yet to warrant that level of spamming but I hope it's only a matter of time :)