Unless you want to print posters of your fantastic whale sharks encounter in wide angle in Coco's, you can surely live with less than 8 Megapixels. However, more megapixel means more capacity to zoom in on details so it comes very handy for macro shots to make them look like super-hyper-macro shots.With these, unleashing the power of Photoshop will lead to superb composition.
There is however a catch... A lot of pixels crammed in a small size sensor generates a lot of noise which makes your pictures less sharp & crisp. Canon acknowledged this in their 'G' series. G11 has less megapixels than G10. Olympus' 14 megapixels series has been shown to produce extremely noisy pictures even under normal illumination (i.e. with the flash).

                                           

Olympus Tough 8000 14Mpixels	Lots of noise in the dark areas	Same shot with a Canon Powershot A85 4.2Mpixels	Far less noise even in the dark areas