I think the problem with the parent describing the symptoms is that the list may well be incomplete for differential diagnosis to take place.
The danger in this situation is of one serious but rare infection buried in a population of common but innocuous ones. The crowd will say "nah don't worry, everyone's got a cold". Hopefully, an expert would discard such assumptions and run through the full diagnosis procedure. In some sense, then, it's perhaps better that the experts *don't* know about something doing the rounds, to avoid a predisposing assumption.
An alternative would be to make the expert systems behind NHS Direct more readily accessible, to avoid the call waiting involved in using them currently.
Great comment. Accessing the NHS expert system is a useful idea and worth exploring. I wonder if combining expert systems with real people makes for an effective crowd.
Overlooking the rare infection is a problem for anyone, including experts, who possibly do it more often than we suspect. Nonetheless, your concerns are valid; using crowd consultation for this application might be problematic.
However, most child illnesses are low grade and I have no doubt that "the crowd" knows how to "diagnose" them. Although, we are not actually talking about diagnosis here, but categorisation: doctors - yes or no?
Parents already make that decision by themselves. I wonder if the crowd solution "improves the process".
The problem remains even in categorisation rather than diagnosis - innocuous symptoms can relate to serious illness.
Fortunately these days, many parents are more aware of the symptoms of meningitis, but it was not always the case. In the case of meningitis, the "crowd" would hopefully give good advice. But less well known conditions would not necessarily give the correct answer - and the ramifications could be serious.
This effect can be observed by watching "Who Wants To Be A Millionaire" and observing that the "ask the audience" voting can often be correct, but can also be wildly wrong.
So, Smart Mobs need to be smart to be useful. I've always found the smartest people are ready to admit when they don't know the answer, so, perhaps the wisest mob would be replying "Try calling NHSdirect" and give you the phone number. 
Of course, mentioning "NHSdirect" is rather parochial for your international readership, to explain: it is a 24hour helpline provided free by the government, staffed by medically trained nurses, who use their knowledge and an expert system to assess the patient condition and provide advice.
Thinking some more on this, I decided that "the crowd" is probably most useful in two extremes: where everyone is an expert or no-one is an expert. If crowds can vote "we don't know", the dangerous middle would be excluded.
Commenting by HaloScan
