I guess the people who are interested enough to go on forums dedicated to this stuff would be fairly discerning and would spot stuff like that quite easily.
Presumably they're not buying the better value bigger bottles themselves and wanting to split them because they want to have a varied collection of them or something?
Actually on another note, as this thread has peaked my interest, half joking post about Lynx Africa aside (though I do actually like the stuff as a deodorant spray) , what do you guys do when a fragrance is no longer made - for example I quite liked a bottle of Dior Higher that I bought a while ago aside from that I've just a few Hugo Boss things from Christmas presents etc.. as I don't really wear this stuff much they've generally lasted a long time, though I recently wore some at a wedding and a girl I was spending a bit of time with noticed it and said it was really nice.
I think the Dior fragrance isn't made anymore though looks like it may be available from amazon sellers... how long do these things last? Is it fine to buy stuff that is quite likely years old and stored god knows where by the third party e-bay or amazon seller? (presumably they do last for years?)