When we were testing with the beta testers the percentage of spam in total comments was about 64%, as of writing this it has risen to over 78% and is hovering near 80% day‑to‑day. It’s been interesting to watch as new people join the network the sheer volume of spam they get. The blog who has gotten the most spam comment thus far has had 99.51% of his comments caught as spam, thousands a day. (And no false positives.)
If email is any indication this is a trend that’s only going to continue. What better time to upgrade your spam protection system to Akismet? š
Akismet 
Bit of self selection going on here, of course…
When I pulled that stats together from the trial period, I was aware that my spam percentage of 74% was higher than the official group 64%.
The reason for my spam percentage being higher was that my blog receives fewer real comments than some of the other trial members (e.g. Matt), so assuming we all get the same amount of spam, the ratio of percentage of has to be higher.
My prediction therefore is that, regardless of the email trend, this figure will rise as more people use akismet to protect low-traffic blogs, because those low traffic blogs get just as much spam as the popular ones.
I have yet to get a false positives but since I’ve installed it has also caught every real comment I have received.
I don’t get a lot of comments to begin with and they did not look suspicious to me so i don’t know why it seems to just capture everything.