I'm pretty sure this means someone hired 3 times 30 user spam-packages, and YoBit is probably the only party that has an interest in doing so.
Unfortunately it's impossible to find out who did it, any legit company shouldn't hire spam bots for "marketing".
Actually, it's not first time when Yobit got involved in similar activities. In past Yobit used ANN bumping services to bump their official thread. You can see it on last pages of thread:
https://bitcointalk.org/index.php?topic=914975.4220It's been cleaned a bit, but you can get image from posts there. This is main reason why their thread got locked. I'm not sure why they can't promote their service in a right way.
How about ALL noob & waking up accounts having to do a captcha on login &/or when posting until X amount of posts are reached - wouldn't that get rid of the spambots?
Captcha for Newbie accounts been propposed many times in past, but theymos probably have his own reasons why he rejected this idea.