The BAA need to keep spotters out of Heathrow as there's not enough room for the passengers, never mind meeters and greeters and spotters.
However if there was, and this is my serious point for a minute, the Police would be able to point people in the direction of a designated viewing area and people would be able to enjoy a little time at the airport, in the open air and away from the juvenile petty hassle that is what passes for aviation in this country.
BJCC - I hear what you're saying and you make a good point as there are some proper idiot spotters however there are a few good uns too. Much like the Police oddly enough.......