I have an SQL database size limit of about 100 MB on my host, and my database usually hovers around 3 MB in size. With recent comment spam, this rose within a couple of hours to over 150 MB and there were all sorts of resulting flakiness (and over-the-limit bills). For now, I have backed up comments and wiped them out. I will restore them after I fiter out the noise, and learn how to prevent such nonsense in the future.
Oh, and spam bot writers — fuck you.