http://steamcommunity.com/groups/trade_tf#announcements/detail/38640603424492664
'What is Escrow?', After a trade has been accepted by both parties, if either party's account has not been secured by the Steam Guard Mobile Authenticator, then to protect against unauthorized trades, the traded items will be placed in escrow. During the escrow period, the items will not be available to either user. This allows users who have not secured their accounts to cancel any unauthorized trades and recover their items. Canceling all pending and in-escrow trades will place a trading hold on your account for a few days to prevent any further unauthorized attempts to trade away items.
When it gets released, it could mean the end of bot trading services too.

petition this garbage
posted in the TF2 thread but i doubt it'll get too much attention there
i didnt know whether or not to put this in games, but it's more or less on the service so i just put it here
if not i'll wait for it to be moved or something
why the forget would you do this stuff, steam
do you not like bots or something? this is why people disliked the whole 'email verification' bullstuff too
and now you're forcing people to use this
what if someone doesn't have a phone that can do this
do you just want to ruin trading for them
ugh