I feel like it was a wave of accounts getting deleted, because I just woke up this morning to see a severe drop in traffic...and come to find out about 50 of my accounts have been suspended overnight. Getting back to work, I am seeing that many of the videos that I post comments to that had alot of spam are now clear of it.
I'm noticing that many of the domains and account names that were flooding youtube with spam are now suddenly gone, so like I said, based off that, my experience, and what I'm reading here it seems like it was probably a large wave of bans.
EDIT: As a side note, I'm noticing something with the comments I am posting now that wasn't happening before. With some of the larger youtube channels, such as ones run by big companies/corporations, my post are sticking for a short time before being completely deleted from each video on that channel. I know that if a channel blocks you, it will remove all comments you have posted on any of their videos, but this is something that wasn't happening to me last night. For example, IGNentertainment's videos used to hold my comments for weeks if I looked into the backlog of comments...but now they are gone within an hour. Maybe they actually have an employee policing the videos now, but it just strikes me as a little odd that this just started occuring for me this morning.