With the exception of UAE nationals, all other residents require permission from the UAE government to live in UAE. All non-Emirati require work permits to be employed in Dubai and UAE. They may be subjected to a work visa or entry visa. Ban depending on who they are and what they had been doing when in Dubai or UAE.
An immigration ban means you cannot enter the UAE, whether as a visitor or for residency. Other bans can arise if you have been convicted of a criminal offence while in the UAE. Common offences that many expats get into trouble with are bad debts, bounced checks, drinking and driving, drunk in public, inappropriate relationships. Of course, more severe offences such as theft, violence, rape, murder etc will also result in an immigration ban but not so many expats indulge in these activities, and those that do are not usually so surprised to receive a ban.
An immigration ban can also arise if you have broken the rules related to immigration for example entering the country illegally, working without a work permit, absconding (leaving your job without informing your sponsor / employer), overstaying (this last one is not so likely to be a problem, just expensive when you get your overstaying fine)
Criminal offences usually result in a permanent ban and this is monitored via eye-scanning equipment at airports, so losing your passport and getting a new one won't get you back in to the country.
