All the casinos I've played in have limited the number of splits to having four hands in play on one spot.
Let's say you get an unusually long run of eights, for which BS says to keep splitting (hey, let's have fun, the dealer upcard is a 6 and the count is through the roof, so it's party time).
You start with: 88
so you split them and get: 88 8
split and get: 88 8 8
split and get: 88 8 8 8
hit and bust the first: 888 8 8 8
so now you have: 8 8 8
and you hit to get: 88 8 8
Can you now split what would have been your second hand, to
8N 8 8 8
(where 'N' is whatever card comes out next, not important now)
or does that first busted hand still count as a fourth hand?