This card intrigued me so much that I ran the following experiement on my computer a couple of years ago:
Starting at 1 mana, you activate this as many times you can until you reach 0 mana. How long will you take?
The result was: most of the time the sequence ends shortly (there's one half of a chance it ends after the very first step), but occasionally (think a one-in-30-or-so chance) your mana pool skyrockets to hundreds before it finally comes back down to zero.
If I recall correctly, it was mathematically proven that the average number of steps this experiement will take is infinity (think arbitrarily large), although every single run ends in finitely many steps. For those interested, google search "random walk".
Posted By:
Gabriel422
(7/28/2011 4:23:54 AM)
I won a game with this tonight with Krark's Thumb and Chance Encounter. Awesome fun.
Posted By:
helluin
(3/26/2011 11:11:08 PM)
The reason it can only be played as an instant, is because mana abilities can't be countered. This ability, however, you can counter using Stifle and other similar effects. On the contrary, mana abilities like the one of Llanowar Elves can't be countered.
Posted By:
GrimjawxRULES
(5/6/2010 3:49:33 AM)
What are the odds of winning a coin flip 
times in a row? The same odds that the universe happened by accident?
Posted By:
TheWrathofShane
(10/20/2012 10:51:54 PM)
why does it say "only any time you could play an instant"
Posted By:
bijart_dauth
(3/20/2010 9:30:15 PM)
I just tested this out normally (by flipping a coin a bunch of times) and I ended up wasting the mana trying to get more, then I tried again pretending krarks thumb was in play and ended up with 9 mana before I got tired of flipping.
Posted By:
supershawn
(4/13/2011 12:20:37 PM)
GrimjawxRULES
You are wrong. It's still a mana ability.
Posted By:
NeoKoda
(11/24/2011 6:14:34 PM)
When I designed this independently, I thought it would be crazy to allow the mana it generated to be fed back into it. So, mine was a red enchantment that could produce 
for 
.
Posted By:
HuntingDrake
(6/9/2013 10:40:55 PM)
Did anyone notice that the color pie in the background is screwed up?
Posted By:
demonknight18
(9/10/2013 2:32:08 PM)
Combos with Look at Me, I'm R&D for infinite mana. (Changing 1 to 0 has some... unintended side effects, however.)
Posted By:
Continue
(11/19/2013 6:38:57 PM)