Valve to add Escrow to Steam?
Escrow is the system, which would hold and store all the items for a couple of days in order to prevent unauthorized exchange, unless one of the parties has the mobile application Steam Guard. During the "storage" period the items won't be available to both parties. The users, whose accounts aren't protected with the application, will be able to return the items and cancel the deal. The cancellation of the exchanges, which wait fro approval or the items of which are "stored", will block the possibility to exchange for a couple of days to prevent the unauthorized exchange of items with the account.
Valve hasn't announced the introduction of the system officially yet. So there's no information on when and how the system will be launched. There's a question on how csgolounge.com, dota2lounge.com and similar services will work under such terms, since they assist thousands of users in executing such exchanges. They will most likely be added on a special "white list", which will enable them to work without delays.
On the one hand, Valve work hard on protecting their users from the account hack and items stealing. On the other hand, some people do have no smartphones. Furthermore, it is yet to be clarified how Escrow operates in the future.