Anyone who's used one knows the limitations of those little pop-up flashes that are built into your cameras. Nearly every photography seminar I've attended tells you to leave them down, rip them off, whatever, don't use them. On a few exceptions, I've been told to use them the opposite of your first thought: turn them off inside or in low light, use them outside or in bright light for fill-in flash.
Those little flashes have a few major problems. First, they're small. That means they have low light output, and are only good close up to your subject, if you're relying on them as the main light in picture. Second, they are built-in. That means that they're optimally placed to give you "red eyes" in your subject, as the light coming from the flash reflects directly back into your lens. Finally, they give very harsh light. This is a result of them being very small sources (nearly point sources) of light, and being directly aimed at the subject. They can really make a nice-looking person ugly.
So, what are they good for? If you can dial down the intensity, they're fine for fill-in flash in otherwise good lighting. For example, if you're taking outdoor pictures in strong midday light, that little flash can fill in those deep black shadows under your subject's eyes, and provide a little catch-light at the same time.
They can also be used to trigger other flashes wirelessly.
nonnit on mu-43.com demonstrated both in his recent post of images shot with a Panasonic Lumix DMC-GF3.
(Click Here) to see nonnit's post on mu-43.com
So, don't literally rip that little flash off of your camera; just use it very carefully.