Read PM

[Spikepit]

A thing in PMs that tells you if they've read the PM or not after sending. Much like iMessage or Facebook IM.
It would be hady in trading situations. The amount of people who just don't reply to trade offer isn't of a simple and polite No thanks is appalling and down right rude.

But it is a bit of a privacy breach too. Maybe a choice to go 'live' or not.