It is 4 this year, but last year, there was a glitch with my ID.
As I was registering for my leagues, I was entering in my 8th league on the same ID, without remembering that the max was 4. Then I realized that there was a loophole in the system. I was curious to see how many teams I could make with that one ID, so I joined lots of public leagues just for the sake of seeing where the limit is. I ended up with 30 teams on that yahoo ID
. It had an error message for my 31st, so I guess it stopped there. Too bad the glitch is gone this season