tri lanes, on the side lanes, are the most common and effective strategy in HoN and Dota, the main reason for that is that the tri lanes usually consist of 2 babysitters and 1 carry, the 2 babysitters just try to harras and get out of xp range, while the carry get all the last hits perfectly (as he has no interruptions from the other team) as well as the xp, and if the other team tries to get some last hits, they are immediately being ganked. however, in LoL, because there is no denying, everyone has flash from level one, spell casting champions scale better, the xp range is larger and its harder to keep the creeps on your side, the loss of xp can actually make it a very bad situation where you have 3 underleveled champions and the risk for the other 2 is minimal as they can just flash out in any sight of danger.
infact, in lol, id say that a good and organised team would laugh at tri lanes and instead of getting pushed and zoned out would just wait in xp range, tick their gold up with gold items and just gank the hell out of that tri lane. even in Dota/HoN it has been established that a roaming strategy is much more effective than a pushing one. there are differences in LoL, which may benefit pushing teams, i dont know, i havent tried it nor seen it happens effectively, but in my opinion the only reason such a team won is because of the surprise factor and the inability of the other team to react to a new situation they havent encountered before.