The Law of Requisite Variety tells us that, the more complex your control of an environment, the more limited the space of outcomes. This is usually framed in a positive manner - you can pin down the response by adding controls - but in a pull media environment, like most social media, that's not a plus. Add complexity to what you say, and you diminish your likely audience.
Google+ has resurfaced the discussion on the purpose of the 140 character limit. Experience tells us that Twitter is a horrible medium for debate, but a fantastic medium for sparking debate.
Keeping messages below 140 characters keeps conversation starters short and open, and that is very fruitful as conversation seed material. It does however also mean that you can only seed conversations. There is limited scope for definite statements that lock a debate down, once a consensus begins to emerge. For that you need to go off Twitter. G+ is designed differently. The entire conversation can stay in one medium. I'm guessing conversations will lock down much better because of it.
Maybe the lack of limits won't matter for G+, because we're used to the short stuff by now, and stick to it for transmittability. But that advantage of course will only last if G+ is a failure, otherwise the new medium will shape the perception of what's possible and appropriate.