My 2cents.

1)I don't care how many accounts per IP address.
2)Having 2 accounts with the same IP address at the same table is questionable at best. Since there is no real money involved I will leave it to the powers that be to allow it or not.

To curb cheating I think the best approach would be to dissallow any number of accounts > 1 from the same IP address at a table if there are less then or equal number of other players.
example a: 2 accounts from IP X at a table should be not allowed (no other players at the table)
example b: 2 accounts from IP X and 1 account from IP Y should not be allowed.
example c: 2 accounts from IP X and 3 acounts from IP E,F,G is allowed.

This is one way to curb cheating. However, this is not really a solution since this can easily be circomvented and is probably why much time won't be spent on it. But perhaps it will prevent some people from inflating their rank. Why someone would go to all the trouble, I have no idea...