Singapore Airlines has announced the introduction of a Cash & Points option to pay for airfare. Yes I was hoping it would look like Avianca's option to buy miles for cheap but it's the opposite – you can redeem miles for a cash booking.
There is a PDF that explains the process which will be available by July 18th.
From the screen shots it looks like the value of a mile will be just about 1 cent. This is the industry average for such options.
This is not an option you should take advantage of. The only exception maybe miles that are about to expire and are too few to use it otherwise (though Krisfleyer allows one-way redemptions for 50% of the roundtrip price).