Well, just to provide a counter-point. I had this kind of setup wit a CPR overflow for over a year, and I never had a flood.
However, the general iffy-ness of the setup made me decide to get regular overflows so I wouldn't have to worry about it. On a tank with regular internal overflows, there isn't any single point of failure. Typically, one overflow can handle the load of the pump, so if one overflow gets clogged you are still ok. I have never had an internal overflow get clogged, though. The only thing I can think of is a really big snail.