Livefyre was one of their early users. Every comment submitted into any comment widget hosted by Livefyre was sent over to Impermium for spam analysis. Impermium had a pretty cool 2 phase process where they'd give you a rough spam score within seconds and then a more accurate score within minutes.

Livefyre had some sophisticated behavior as a result. Comments were always pushed live to other page viewers immediately while simultaneously sent to Impermium, then revoked (via live update) if either the first or second pass through Impermium resulted in a spam indication. Email notifications weren't released until the second pass indicated nonspam.

Not sure if Livefyre still uses Impermium today or what this buyout may mean for them, but I always thought the concept was pretty cool.