All this is true, but has no bearing on the common use of language. When a trader refers to Acme corporation as an $N company, he is indicating that $N is its annual revenue, not its market capitalization.
Common usage that I've seen is to refer to the market cap as the value of the company. For a random example http://www.fool.com/investing/general/2010/03/19/how-does-ap....
The other common usage that I've seen is to refer to a company as being worth X billion a year. In that usage the a year bit is not dropped, because dropping it would introduce confusion with the first common usage.
But when I Googled for "billion dollar company" then "million dollar company" the first usage I found that wasn't in some way tied to startups was http://www.goodnewsnetwork.org/most-popular//red-mill-goes-t... where it clearly refers to revenue.
Ah well. Around here there is no question which usage is more common.
PS You may be amused that the top hit for "x billion dollar company" is http://hackerne.ws/item?id=2033232 which involves you.