It is illegal in the UK to claim that one has a "patent pending" over an idea if one does not
however producing a successful patent can be a costly and time consuming process
so my question is, could you produce a very flimsy application that will most likely be overturned, simply for the purpose of granting "patent pending" status?
this would ward off any potential copiers of the idea for a period of time until the patent is refused
Chris' good link appears to cover most of this issue off for you.
The added point, I think, is that I reckon a fair few organisations use the patent pending concept to 'buy time' - because it enables them to manufacture something that may be infringing another patent for a while OR it may put another organisation off from starting work until the patented element is disallowed. Provided one has actually applied for the patent, this appears to be 'within the rules'.