I remember playing this in my annoyance deck. I
enchanted a ton of my opponent's cards. Then he
was either taking damage from them over being
forced to use the cards in some creative way.
However, I can't see any other scenario that is
really beneficial to you enough to play Power
Leak.
What a pile! Under no circumstances should
anyone ever play Power Leak; it is a complete
waste of cardboard. So you *might* be able to
deal some damage to your opponent *if* they play
an enchantment and *if* they aren't willing to
pay a couple of mana during their upkeep. If
either of these circumstances isn't met, then
you have just officially wasted a slot in your
deck that could have helped you win the game.
I'm a bit disappointed that we can't rate cards
below a 1.0 here, otherwise, I think I would
give this card -- all formats -- 0.5 or so.
An Enchant
Enchantment! One of the more rare form of
spells. Power leak is interesting, but
really not that useful, unless your opponent
is playing a very slow and/or mana intensive
deck that relies on an enchantment.
So, if you're
both playing Power Leak, you could Power
Leak his Power Leak, and vise versa....gets
kinda weird. But, since there really is no
reason to play Power Leak, I really wouldn't
be concerned about it. ;)