Most ad networks used in bitcoin sites pay in bitcoin, not in $.
So they don't need to - and can't - buy new bitcoins.
So the price won't increase.
Not really, i know only 3 major ad networks that pay in bitcoins, most of them are $ based ad networks.
However even if your theory were correct, it still increases the demand of Bitcoin, and eventually it's price, since Labour+Demand = Money, and any demanded labour invested into Bitcoin will eventually increase it's value.
If we can also help the bitcoin ad networks, then more $$ based people will be interested in advertising with them since they offer cheaper ads and a wide range of audience , so they will buy Bitcoin eventually.
So in either case it's a win-win scenario.
