They are more than welcome to
There will be quite a few willing to step in DoubleClick's place. Usual suspects from Seattle, Yandex, Baidu - you name it.
While there will be a temporary inconvenience and upheaval, on the balance of things DoubleClick is NOT irreplaceable. This is a natural consequence of building your offering on top of open source tech - the barrier to replacement (aka barrier to entry is lowered). Presently the sole thing which prevents new entrants into the market is the sheer size of DoubleClick (that should be the correct name of the company based on ideology and behavior) and contractual obligations levied on all Android phone manufacturers. If that is removed and DoubleClick buggers off to pastures new... Well... I give it 3 months for the niche to be filled.
It will also be a positive development as the new entrants are likely to be playing by new tax rules, not by "move all of your income to a Double Dutch Irish Sandwich in Virgin Islands".
Biting the hand that feeds IT
