You really don't need too much zoom here, only around 2x or 3x would be more than enough. In fact, if you're taking a picture of a large group, it would be better to have a wide angle camera. If you're trying to get detailed candid pictures in a party, you would again be better off to walk just a little closer than use a super-zoom camera with a narrow perspective that might distort the picture at the slightest movement.
Pictures of nature need you to be very still to eliminate the distortion, which means you'll have to stay a little back if it means getting a stable grip. If you're out hiking, a camera with a 5x or 7x optical zoom would be your best bet. It will get you the perfect still, without compromising on a larger perspective or on details.
You will need a great deal of optical zoom, at least 10x. If you're taking single subject pictures without much interest in the surroundings, then a narrow perspective camera with 10x or 15x optical zoom is excellent in getting the right kind of detail, like the lion's eyes or the eagle's beak.
If you're taking more indoor shots, you will find a lack of space trying to step back, getting the right perspective. Again, a low zoom (2x to 5x), wide perspective camera would be excellent. If you're taking an outdoor shot, space won't be much of a bother and you'll also want to take pictures of things far away. This calls for a larger optical zoom (5x or more) and a decent perspective.
The answer kind of merges with the above situation of indoor photography. If you're outside in natural sunlight, a good zoom is not really necessary if the subject is close enough. If you're inside however, this means two things; poor lighting and the restrictions on flash. It is a little rude after all, to throw a flash into a person's face indoors in poor lighting. Here, you'll need a good enough zoom of around 10x or 12x to get close-ups without having bad lighting get in the way too much.