This is a completely worthless, and to a large degree thoughtless, observation. A flag in a random situation is random, because, being a random situation, there is no knowledge as to whether complimentary factors are confirming or disconfirming. A flag within the context of a confluence of confirming market signals, on the other hand, is a whole other matter entirely.
When all four rise simultaneously, bad moon rising Via http://www.mercenarytrader.com/2012/11/the-four-horsemen-ride-again/
Larger time frames have more weight... and sideways action will result in a similar assumption ... bear flag forming could be as well