Well the main one perhaps is that beneath the surface it is still a backwards, regressive society/culture and there are ways that this can affect you negatively, in some cases very negatively.
I guess other reasons include not liking the heat, that almost everything is rather fake over there, plenty of people don't stay long/friendships can be rather temporary and actual emigration isn't really possible - even if you do end up working there for decades and make it your home you're still just an expat staying temporarily.
I've got a former colleague over there who loves it. It seems like it can offer some additional cash/nicer lifestyle in some cases - being a teacher the additional money aspect probably is applicable in your case. I think in other cases people are attracted to it as they can't get the equivalent job/responsibility in the UK/Europe and in some cases I think people get duped a bit, like they're offered a job that actually pays a bit less (gross) than they currently earn though perhaps represents a modest pay rise when the recruiter sells them on the tax free aspect and relocation package. I'd only be tempted if a really fat pay rise was on offer.
I'd definitely dispute the view of the poster above who is advocating you ignore negative comments, never a good idea to do that. You've got to keep in mind that plenty (if not the majority of tourists) to the country break the law when visiting, the main ones can be through drinking (illegal for tourists) and taking photos in public with other people in the shot others less common include being gay and having gay sex, taking drugs, using prostitutes etc...etc.. 99% of these people will do all that and get away with it with no consequences and the authorities don't care however if they upset the wrong person/authorities get called then they can end up in a whole world of ****.
For someone employed there there can be more trivial things like getting involved in a car accident with a local Emirati even if it wasn't your fault, you might well need to suck it up and take the blame. Bouncing a cheque is another big one - debt in general can get you into trouble as unlike the UK it isn't just a civil matter... also the way banks work is rather different, your account can be frozen if you lose your job etc.. that in turn can cause you to get in trouble. These are the reasons behind the images you sometimes see of cars (usually super cars but applicable to cars in general) abandoned in the desert, in a carpark at the airport... they're not the product of rich Emiratis with more money than sense but rather they're dumped by expats who have needed to get out of the country very quickly.
