It happens so rarely its hard to replicate to find out what causes it :(
One online invitation - two new games
Boris,
If you enjoy challenging strangers, you might challenge this member to a game: http://www.chess.com/members/view/Angelica_Pickles
They were having the same trouble. I wanna see what happens when the two of you battle! Hehe, might be fun.
I was joking around but you never know, it might produce something interesting. I looked hard between your profiles for anything in common and couldn't see anything.

You need a label for this effect - then you're halfway to solving it. How about the Inverse Thunderdome Syndrome? ("Two men enter; one man leaves.")

I speculate that the reason that causes it may be that your two opponents accepted the seek almost simultaneously. So that the information
"the second opponent has accepted the seek"
happened to arrive at the chess.com server between the arrival of the first accepting opponent and the point of time when the game with the first opponent had been created and the seek had been removed.
If this speculative guess is correct, the probability of three games will be even much smaller than even the probability for two such games, so no danger at all that 12 games are created at the same time :-) .
Hi to everyone,
just out of curiosity: I've set up a new online game and when I got back I had two new games running... Is this normal? I mean I don't have a problem with that, as long as I don't have to cope with a couple of dozens of new games
P.S.: Cool site!