User blog comment:Megames1/Against the Meta: Mega Farming Z Plus More!/@comment-3450702-20121013153925

The reasons we have two solo top champs against each others is that they can each get full farm in lane, while the junglers get additional farm from the jungle and can pressure all lanes. However, 2v1 top, if the 2 are well coordinated, means:
 * The solo top gets little to no gold in lane, and the 2 people on top get more farm together than the enemy jungler, actually moving him ahead
 * The lane is hard to gank, since it's 2v2 and although the solo top is higher in levels, the 2 are usually better farm and thus equipped
 * The tower can be pushed down very fast if needed, one of the soloers can turn to semi jungling after securing an advantage for their lane buddy etc.

Ofc the jungler can still pressure the other 2 lanes, but whole teamcomps can be built on winning hard early to negate that.