49 new members in one day

one day i just get bored and watch statistic forum, and i saw that many members join that forum in this month
next step i watch on members>joindate segregate and i saw, that something around 50 members join that forum in 3 june, some of them have TA:K style nicks (old players, units etc), somebody mass invite old people? or it's just ?spambot?

BTW (only 1 have last counted login)

Edit (28 june)
http://kingdoms.heavenforum.org/memberlist?mode=joined&order=DESC&submit=Ok&username
http://kingdoms.heavenforum.org/memberlist?mode=joined&order=DESC&start=50&username

I've seen the list of all players who have joined, and many are old players I recognize, but they never end up posting anything. And I know we have gotten spambots around, but I've banned them all.