Im starting to think optical zoom cant be too important because a lot of high end cameras have low optical zoom compared to some cheaper models.
If its so important why has the G6 for example only got 4x optical instead of 10x?

It depends on what you want to do wth it. If you are only going to use it for family snapshots and such then it isn't important at all. However if you want to photograph wildlife, sporting events and things like that, then optical zoom is very important. I think it helps alot with landscapes too.

As far as cost goes, the cheaper models may simply have a lower quality lens; so even though the optical zoom is greater, the lens itself may produce poorer quality pictures? But I'm not sure.

be very careful you try out the high zoom cameras, my friend got a cheapish one with a 10x and it took about 4 seconds consistantly to focus in normal room light, and had probably half a second delay with everything it did. make sure you try out what you buy to see how it feels

There are many reasons why cameras are designed with different lenses, the main one being different market segments. Not to mention size/weight and cost, and of course, overall optical quality. It's very easy (and cheap) to make a small, fixed-focus lens (disposable 35mm, etc). It's very difficult and expensive to design a high quality long zoom with decent aperture throughout the zoom range (Panasonic FZ20, Canon S1IS).
Also, while the G6 is indeed a fine prosumer camera, the current flagship Canon is the Pro1, with a 7x zoom. Nikon has recently released two 8MP cameras that are their flagship P&S models, the 8800 and the 8400. The 8800 has a 10x (35-350mm) while the 8400 has a 3.5x (24-85mm). These two are fairly close in price, but have vastly different lenses. They appeal to different markets for excellent cameras, whether the user needs expansive wide angle (24mm) or narrow, close-up zoom(350). It would be extremely difficult to make the 24-350 lens, so there are 2 separate cameras.

I find zoom to be very important, but I wouldnt overdo it. A 3x zoom would be similar to that of a standard small telephoto lense that would be packaged with your SLR body at the corner store and is probably sufficient. If you want more, a 7x or 10x would of course compare to a large telephoto lense. Zoom is important to me because its not only good for closing in on a far away subject as Sam suggested, but also for creating precision and intentional composition. Its essentially cropping the photo without using photoshop, a film enlarger, or scissors hehe. The larger the lense (or greater the zoom). the more potential for cropping. Just watch the shaky hands (or use a tripod) when maxing out that zoom.

I use an S1 with 10x zoom. In an informal poll of my shots, roughly a third are at full wide angle (38mm), another third are at full tele (380mm) and the remaining third fall somewhere in between. Many people will use as much zoom as they can get.

For me zoom is all about potential and keeping your options open. My "flagship" camera, that is the one with which I shoot most of the shots that I wind up uploading has a 12x zoom. Now most of my shots, as with xentrik are done in the 4x-6x range, but if you don't have a powerful zoom lense you will never be able to get the shots at long range. The 12x zoom is nice, but I will definitely need more.