I am sure they’ll say it was just one small incident:

We know so far that the stimulus signs cost from a few hundred dollars to as much as $10,000, which was the cost for the giant billboard that adorns renovations underway at Washington Dulles airport. The Washington Metropolitan Airports Authority confirms that the $10,000 was diverted from runway resurfacing. With 190,000 projects having been funded by the stimulus, tens of millions of dollars have probably been spent telling Americans how their money is being spent.

If stimulus funds are used to displace work within a stimulated project, is it really that much of a stretch that these funds are displacing productive private activity?