Most effective antispam/antisplog plugin available

Anyone with a WordPress installation running Multisite, Buddypress or any site accepting user generated content needs this plugin if they aren’t to spend half their life getting rid of dodgy users/bots intent on posting spammy content on their site. The effect of installation is dramatic in that it will scan for likely spammers already registered as members and act as a barrier to new ones coming in. We run a multisite setup where the business model is predicated on users being able to join and set up legitimate sites but we don’t want splogs or spam comments. Cleantalk seems to achieve this goal without Captchas, silly sums or any other barriers and it seems to manage it without any significant numbers of false positives and very few missed spammers. By far the best plugin we have found for dealing with this problem. Paid-for, but at $8 a year for a single site it is an absolute bargain that will save you hours of work and a lot of embarrassment.