Truth is, squats, when done properly, are much safer than a majority of isolation-type movements, machines and, yes, even leg presses (to correct depth, doing the leg press can very much damage the low back).
There are many ways to tailor the squat to one's specific athletic/aesthetic requirement. I mean, the one poster who suggests squatting will make you appear as a gigantic SPF-type powerlifter is clueless. There is a WORLD of difference between performing Olympic squats with 315 and doing power-styled squats out of a monolift with 800 pounds.
Squatting is for truly athletic men and women.
I agree - squats are great. Maybe THE greatest exercise for strength and mass...ok, maybe second behind deadlifts. But that's semantics.
However, most don't have the hip mobility or thoracic spine mobility and strength to squat properly. Most don't have the core strength necessary to brace the abdominal wall and keep a natural arch to the lumbar spine at full depth. What's more, most don't have abductor strength necessary to keep the knees from caving in, which can erode medial collateral ligaments in the knees. Furthermore, the least bit of imbalance between the feet can, over time, put a serious hurt on the hip joint (i.e. one foot points in or out slightly more than the other).
Squats are great, no doubt. But the risk for injury is high if you don't do them right. I suppose you could say that about any exercise. But given the loads most are prone to using in the squat, we can see that there's no margin for error; if your form isn't bang on, you can really get hurt a lot quicker with squats than you can with lunges, let's say. It's much harder to hurt yourself with dumbell curls, for example, because the load is too small to really kill your joints unless you get stupid (apples to oranges, I know, but you get it).
For hypertrophy and strength, it's hard to beat the squat when done right.
But since many, many guys can't squat right (though most won't admit it), there are safer moves. I like single leg bulgarian split squats, which take unilateral imbalances out of the equation and allow the body to move more freely even with imbalances. And, if you can hold a couple of 120lb dumbells in your hands and do 1-leg bulgarian split squats, I'd say you've probably got solid legs to go with it.
Again...no slam against the squat. I used to love it, and still do. But it's so easy to hurt yourself unless you're really in tune with your body and the mechanics of the lift (like most powerlifters and oly-lifters are), or you have a good coach who's taught you right from wrong (i.e. not your buddy at Good Life Fitness or the trainer at Planet Fitness).
