Well, as stated by Kenney_Leong, with no flash, any automatic camera trys to compensate by increasing the ISO & slowing down the shutter speed as much as it can. (without the user knowing what the camera is doing)
This is where cameras differenciate themselves, by some having 400 or 800 ISO max (but noise problems), shutter speed from 1/1000th of a second to 30 seconds exposure or more, and of course the size of the lens itself plays a huge role in these conditions (bigger lens = more light getting to the CCD sensor faster).
I have a Sony W1, which is a semi-manual camera. One example I can give is I take all my Birthday pictures with no flash & longer shutter speeds. This gives a very nice glow to the candles & a warm picture. Whereas with a flash, the candles just seems to dissapear & the "ambiance" of the scene is gone. However I would recommend a tripod, or at least leaning on the wall to help steady your shot. (This is where you will get motion blurr, due to the long shutter speed).