As far as I know it's not banned in any format where those cards are legal, although if you play casually the group you play with might have something to say about it, although it is fragile enough to not work every single time you get everything on the board.
I have been the object of much hatred after I pulled off an Altar - Saproling Cluster - Fecundity kill combo in a multiplayer game. (mill through your deck and build mana with the combo, find and use Squallmonger and Urza's Armor as the kill)
We're Coming Back!
We would use a Sliver Queen to generate alotta sliver tokens, then kill'em off with the altar to produce enough mana for a fireball or blaze.