anjohl: No offense, but I don't think you know much about weightlifting. A gym is perfectly safe as long as you work up to free weights. I wouldn't get a new lifter with no experience to do deadlifts or clean and jerks, but a nice 5-10 machine circuit is not going to hurt anyone providing they understand that the weight should be under control at all times.
Also, a workout partnership will lead to knowledge, as you both will play off each other. The average Joe can get more from Arnold Schwarzeneggar's "Encyclopedia of Modern Bodybuilding" than 100 times it's cost in personal training sessions. MOST personal trainers have very little strength training experience, they are just motivators. Motivation ultimately comes from within, and if you need a paid trainer to motivate you, the fat will wait patiently for you to run out of personal training money, trust me.
I used to lift weights and yes, the gym machines are far more dangerous than their free weight counterparts. For the simple reason that they force your body to conform and everybody thinks they know how to use them. What's more some of the machines can't be used safely.
As orcishgamer pointed out, there are a lot of people who think they know how to do a lift, and are wrong. Most folks suggest that you stop doing your squat when your knees are over your toe. Unfortunately, that's wrong, but extremely common.
http://www.bodybuilding.net/training/knees-over-toes-myth-12253.html As far as that encyclopedia goes, it's bullshit. Body building is not something anyone in their right mind engages in. It's about creating showy muscles via isolation. And yes, if you want to be Mr. Universe that's what you do. But, it's the exact opposite of effective.
As far as weights goes, power lifters are the ones doing all the interesting stuff. Body builders are best ignored.
anjohl: I think a big part of the aversion is the culture. It's about false promises, false hope, sales, and the illusion of knowledge.
Most personal trainers know very little, and the extra results they provide at 10x the cost per zession than going it alone or with a partner do not deliver anywhere near 10x the results.
That's why you make sure that they're qualified to do their job. Apex or equivalent plus ACSM is really the bare minimum to even consider a trainer. And ideally they'll have some sort of masters in nutrition, sports medicine or similar. On top of that, you're going to have to do some homework in order to make sure that they really know their stuff.
But, even with just Apex and ACSM the chances are quite good that they know more than the idiots hanging out at the gym.
Ultimately, it's your body, it's your responsibility to perform due diligence when taking advice on how to care for it. Making over generalizations isn't going to help anybody.
At least with the trainers there's some basis for the advice. All the materials I saw when I was starting out down that road were based on research. It wasn't always great research, but it was a hell of a lot better than the crap I've heard so called gym experts spouting off.
The worst information that I was presented with has been merely ineffectual. I've seen some incredibly dangerous advice handed out over the years on the basis of gym lore.