(frame rate *cough cough*)
Right. Framerates would take a tremendous hit. If you have ever seen the in-game flames and examined closely, I'm sure you would have noticed that they are simply a trail of 2D images repeated over and over in given intervals. This is why our framerates don't take a massive hit whenever we hit something with guns, are leaking fuel, have air show smoke on, or something with bombs, rockets or DT's.