Comments spam is getting more and more clever. I just had one which took a minute and a half to classify properly as spam rather than a particularly wordy example of the product of an addled mind. It was semi-on-topic, filled with hot-button phrases aimed squarely at the political slant of my particular blog; if I only scanned for ideological relevance, it might have gotten past. Sadly, once you actually try to make sense of it, it's clearly a very clever example of word salad with embedded advertising links.
But they're getting closer.