That's usually called "the broken window fallacy".

A kid goes out and breaks random windows in people's home; as a result, a lot of economic activity ensues - the glass producers, the people who produce glass cutters and specialized tools, the people who install windows, the cleaners who specialize in cleaning broken glass, etc ...

The ad industry is breaking everyone's windows. It does indeed produce a lot of economic activity; But it is more likely than not "misallocation and waste of funds" when looked at in a broader context.