Wirelessly posted (BlackBerry8520/4.6.1.314 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/125)

Blinds were all down on a BA flight at Rome last week when we boarded - it seemed to be a new thing, because the crew were discussing it while we waited for the second bus to arrive - their view was that it had made a big difference to the temperature in the cabin.

As others have said, it's a regular thing at airports in the southern US - AA usually ask passengers to close the blinds before disembarking at DFW, MIA, ATL, etc.