If they're on a spouse visa, for them to be deported, they need to be sentenced to a year or more in prison, or they need to get a drug conviction - and even then a good immigration lawyer can sometimes get the deportation quashed on the basis of the constitutional right for families to reside together. This is why they altered the immigration law to allow them to simply revoke spouse visas if they appear to be false marriages.
As to citizenship, once you've got it, you've got it. The only reasons it can be revoked is if you are found to have submitted a fraudulent application for naturalisation, or to have wilfully maintained a second citizenship after naturalising. Being charged multiple times is more likely to result in you being investigated very thoroughly, though, which would turn up if either of those cases was true.
Oddly, it's easier to be naturalised than it is to get permanent residency.