But what if one wishes to use Nimzowich's idea of prophylaxis, that is, trying to stop your king from getting across before attacking with mine?
Bongcloud Invitational!

You could try that, but it will not necessarily work as well.
Yeah, but if I'm allowed to do that, then why is checkmate counted as a loss?

Because the goal is to get the king to the other side, not to checkmate. Some of these variations can be quite bad if checkmate was not disallowed. So the rule exists.

Because the goal is to get the king to the other side, not to checkmate. Some of these variations can be quite bad if checkmate was not disallowed. So the rule exists.
So a sort of Sofia rules system that forces aggressive Bongcloud play? Ok, I'm game, as long as its unrated.

This sounds fun! Count me in.
EDIT: By the way, what's the rule regarding perpetual check?
It's a Draw -> Black Wins.
Anyway, I'd change this rule. Black could force a perpetual, get the Draw and move on.
I would like to announce a new tournament has been opened!
The First Official King of the Hill Bongcloud Invitational!
Post here to sign up! This will be a knockout format tournament, 3-days per move, unrated games to ensure people do not play the system.
Note: Checkmate is not considered a victory. In the event of checkmate, the result will be in a loss to the player giving the checkmate. The only way to win is to march the king to the other side of the board. In the event that there is a draw, black will be given the advance to the next round.
At least 8 players will be signed up, 16 if this tournament is very popular.
The game links will be in the forum so others may watch.
The players listed as playing white will issue the challenge to the player in their pairing. When the game is complete, message me the results so I can verify.
If you have any questions, concerns, or need adjudication, message me as well.
The winner of the tourney will be named the king of the hill and may wear King Lenny's crown with pride.
You must use one of the openings out of the Bongcloud Opening Book. It is provided below on post #1:
http://www.chess.com/forum/view/chess-openings/bongcloud-opening-book?page=1
Round 1 games
Pauix vs soothsayer8
bjazz vs duskrevival
StephenHough vs yousef213
ChenYakumo vs TheMouse
mrguy888 vs jetfighter13
Mushyrulez vs oinquarki
sammy345 vs jerry2468
ivandh vs IWishIWasSmart