I'm sure it won't put a stop to it, I love to read discussions about "Does company X engage in anti-competitive behavior and are they a big enough player that it's a problem". That seems to be a much more useful discussion (i.e. it gets at "do they need to be reigned in by We The People") than "are they a monopoly" which is just bickering over what words mean (with some shades of "if they _were_ a monopoly, then We The People should do something about it).
At the end of the day, who cares if they are a monopoly or not - you don't have to be a monopoly to be in a position to do Bad Stuff to The Market.
> if they're a monopoly, then they simply shouldn't be allowed to exist.
Market driven de-facto monopoly are allowed. If you own >90% search engine marketshare it is fine as you have earned it. If you abuse the marketshare to enter shopping, travel market it is monopoly-*abuse* and it should be blocked/fined.
Abuse would include if you were charging ridiculous amounts of money for your monopoly service, like Ma Bell did, right? What about deterring competition with portfolios full of braindead patents? Buying legislation that puts high barriers around the market? I think the separation between government and big business is a farce, today, and in combination they're way more oppressive than high priced telephone service was way back when.
At the end of the day, who cares if they are a monopoly or not - you don't have to be a monopoly to be in a position to do Bad Stuff to The Market.