While not as ideal as fixed pinned OCF, bounce flash is still a solid go-to for lighting toasts and speeches during a wedding reception (so long as the reception is being held indoors in a venue with bright ceilings).
With bounce, the on-camera flash becomes the main light while the off-camera flashes act as rim lights. That said, the distance between the on-camera flash (or you the photographer) and the subjects will determine in large part how much light reaches the subjects. Of course, you can adjust flash power and the zoom on the flash, but that will only get you so far. Having to shoot within a given (often tighter) space can limit creativity when using bounce flash.
Because of the close proximity needed to use bounce flash, photographers should be mindful of how long they occupy the space needed to capture images. We suggest getting in, getting the shots, and then stepping back out of the area so as not to take too much attention away from the toasters!
Tip: Watch the details! Chimp for odd flares & shadows.