The only problem with market cap as 'value of a company' is when silly things happen on the market like a company gaining 300% of it's value in under a month and then promptly losing all of that a month or so later.
Personally I don't buy it. Market Cap is just what 'the fools want to give for it' (to paraphrase a Dutch proverb) and is way to fickle for an actual display of the value of a company in monetary terms.
I'll grant you you'd need that much money to buy 100% of the company from the investors (more or less anyway) but please realize that the market cap is not even money or assets in the hands of the company itself, nor are low/high shares particularly required for a company to operate. (only time it really becomes relevant is when they give out new shares which usually does not happen all that often)