motorhaven - 4:13 am on Jul 29, 2012 (gmt 0)
I do some selective blocking in 8.x.x.x, nothing in 4.x.x.x.
The 4.x.x.x I show literally thousands of posts from long time forum users (as opposed to single post users which would indicate spammers) in pretty much every single 4.x.0.0/16 range. It looks like its a huge dynamic IP pool for broadband, because the same user will bounce around between 4.x.0.0/16 addresses over time. I would lose a huge amount of legit traffic blocking out this range.