Knowing what kind of chart is the best to use in a given situation is an art as much as a learned skill. We've all seen flow charts that have been created just because someone thought that a flow chart was a requirement and shoehorned one into the presentation. Flow charts and decision trees have their place, as do bar charts and pie charts. But using them in the wrong place with the wrong data can not only be ineffective, it can be misleading. A flow chart that has nothing to do with process flow is really just a set of figures connected by arrows. If time and steps or stages are not involved, what are the arrows representing? It might be hard to abuse a decision tree, but our friends the bar and pie charts are two of the biggest liars out there.
Surprisingly, I'm not seeing as many graphs as I used to in internal corporate communications. Perhaps their abuse has led people to simply keep with tables of data.