The problem people have with utilitarianism is that it does technically allow a majority to abuse a minority for the greater happiness. If, for example, a small group of people could be enslaved in order to provide luxury for the majority, that would add to the overall happiness and therefore be right by utilitarianism. So clearly, a rule is needed which can stop the exploitation of a minority in order to increase the happiness of a majority, without ruining the whole framework.
I think the solution to this problem is consent. If a minority (however small) is in a position where they could be made to suffer in order to increase the overall happiness, they can’t be forced to suffer in order to make everyone happier, because they haven’t given their consent. I think adding consent to the utilitarian framework covers the problems it had before. If an action can only result in happiness, then yes, it is the one which must be taken, but if it will also causes suffering, then consent needs to be had first, before the action can be undertaken.
(Don't miss today's Finger Puppet Show!)
(Also, be sure to read Bath Spa University's 2014 anthology Writers Unblocked, featuring five pieces by me!)