Same here. Myself and two other friends were so hyped when D3 was unveiled we went and bought D2 battleschests to play. After a few time of disconnects and temp bans, we thought it was bnet doing maintenence, server down, or what not. So sure enough with high hopes, still hyped, we waited. was later that I realized Blizzard has implemented this some time ago.
Well, it turns out if you create/join/relog too quickly and often, you will get 'temporarily ban.' As for the of of time varies. It is defintely not 5-10 as Blizzard states, sometimes it can last up to hours if you do Baal runs too vigorously. So NO Baal runs, NO meph runs, NO xfer that doesn't last upward of 10 minutes or more. If you do any of the above under 10 minutes, ur heading closer to temp ban each time. Blizzard stated that this was implemented due to the high amount of botters. But it mostly annoy non botters. Botters and spammers seems to be bypassing this easily though.
It's bullshit, but what can you do? It is free afterall, or is it? But hey it's free online service, why should they give a cow's ass about fans and loyal gamers, right?