ooo - touchy.....
so - if you'd tried them out - how many had you taken and over what distance??? and did you get the shits?? and was it a race??
it's not necessarily true that you took too many, but I think most of us would say you don't NEED to take 4 on a 1/2 and many of us (me included) wouldn't bother at all as you should have enough stored glycogen to do a 1/2 provided you keep hydrated....
and don't assume on the basis of one experience of the shits that the gels are to blame - if it was a regular occurence when you take them, then yes, I would suggest a pattern but on the basis of info so far - not enough info!