I'm a bit pissed off with Valve/Steam right now.
The sale ends tomorrow, and I have a couple of extra cards from the Steam Summer Sale that I can't do anything with. Trades take 24h to complete, so that's a no-go as the cards will vanish before the trade is completed. And it turns out that I can't sell them either because to do so, I have to give them my cell phone number to activate the Steam Guard thingy, or else the items will be held in custody for something like two weeks.
When did that happen?!
Oh, and to be clear, I'm not giving Valve/Steam my cell phone number.
I think it's to get rid of all the bots that plagued the market previously, and it seems to have been relatively effective at doing so (judging from the volume on commonly traded cards like the L4D cards.)