No you're right Jim, many of these one can see through but their popularity is such that there must inevitably be a success rate - and it could easily be one of our own that is hoodwinked by something more convincing.
We talk at times about having one's faith restored in human nature but these antics are exactly the opposite and something we have to be constantly educated about as the tricksters become more sophisitcated..
Apparently "origin" telephone numbers (ones which are either displayed on the phone screen or revealed by dialling 1471) can also be faked...what looks genuine is in fact a piggy-back to another concealed number