Nature reports that promiscuous voles can be made faithful by the addition of more hormone receptors in the brain. The hormone in question, vasopressin, appears to be produced in large quantities during sex, and seems to encourage bonding. And though they caution that pair bonding in humans is vastly more complicated than in voles, the idea of transferring this to human relationships is definitely there.
The BBC report gives a slightly different take on it. Autists have difficulty bonding, so maybe through vasopressin we could find a possible cure for autism.
Both are tempting ideas. We could cure infidelity, or autism, through hormone treatments. But first we have to decide what is a disorder, and what is natural. It would be far too easy, once we have a cure, to define anything other than some theoretical ideal as the disease. What's the difference between an autist and someone who just doesn't like chatting much? How many partners do you have to have before you need treatment for promiscuity?
Some people say we're already in this situation with antidepressants such as Prozac (given, according to some, to anyone who might be a little unhappy), or Ritalin to treat attention deficit disorder (or, perhaps, any child that doesn't sit still). On the other hand, some people say that both these drugs are underprescribed, and many depressed people and hyperactive children are going untreated. (Both sides of the argument can be seen here.) Here already we see the problems of a fuzzy boundary. Where diagnosis is based mainly on personal judgement, health professionals need a lot of time spent with the patient to work out what's going on -- time which they rarely get. More importantly, we need alternatives to the drugs, for those people who need something other than a chemical fix. And this will also be true if we develop a drug to treat autism.