Here is an article written by the BBC in the UK stating that google has changed there policy so that you are unable to sell gmail invites. Check it out: http://news.bbc.co.uk/1/hi/technology/3859501.stm
Seems weird that they would pay - but there are worse buys... a pet rock, a richard simmons workout tape, and a computer with Windows installed on it are a few good examples..
Yes some people are getting greedy and money hungry but also stupid. But also people dont know what to do with there money. Well that is my opinion.
Why do you call the people selling it stupid? It's just like selling anything else really, whether tangible or not. If there is a market / difference between supply and demand, then there is a price. If there are people willing to pay that price (regardless of their intelligence or wahtever) then to me it's perfectly fine to sell it. When you have sold it then you have satisfied both party's needs. It shouldn't be done though if it indeed is unlawful.
Invites were fetching good money a few months ago. $50 in some cases. I think I even saw some for $200. Now they go for like $1 or $2. With this policy change I wouldn't be surprised if we start seeing them all disappear.
But I see g-mail invites being given away all the time - who would buy one anyway. Just look around....