A drop in search volume doesn't impact their content network ads, you are correct.
However I don't think Microsoft will let Google buy space on Bing to place their ads. Therefore a drop in search volume leads to a cut in ad revenue.
Even if placement on Bing for ad words was possible Google would have to give Microsoft a cut - right now they keep 100% of search revenue (minus operating costs). Unless Bing is substantially cheaper to run than Google that would work out badly for revenue per ad.
Worst of all from their perspective a drop in search volume would lead to a loss of opportunity to push news, gmail, youtube and especially maps/local search. These related properties must be benefiting heavily from their top placement in Google search results.
However I don't think Microsoft will let Google buy space on Bing to place their ads. Therefore a drop in search volume leads to a cut in ad revenue.
Even if placement on Bing for ad words was possible Google would have to give Microsoft a cut - right now they keep 100% of search revenue (minus operating costs). Unless Bing is substantially cheaper to run than Google that would work out badly for revenue per ad.
Worst of all from their perspective a drop in search volume would lead to a loss of opportunity to push news, gmail, youtube and especially maps/local search. These related properties must be benefiting heavily from their top placement in Google search results.