How about:
"Hi, this is facebook, this time we've really learned from our past mistakes.
I know you've heard that before (several times in fact), but this time we actually mean it and we'll show you how and why.
To begin with, from now on we will detail the commercial activities that we engage in with your data and we will allow you to say yes/no to every individual transaction. We wouldn't be a commercial entity if we didn't find a way to make that to our advantage though, so here is the deal: Every time we have a commercial proposition you get a link in your email and a notice on your wall. You can configure to default 'accept', 'deny' or 'hold until confirmation'. If you default to accept and you do nothing the deal is on. If you default to 'deny' then the deal is off, unless you decide to accept anyway through the link on your wall. If you default to 'hold until confirmation' then you will only be able to proceed after the terms and conditions of this particular deal have been made clear to you and accepted by you through an extra confirmation step.
Our advantage in all this is that we hope you will visit facebook more frequently to check up on us.
Of course we hope that you will trust us with your data, but given our recent antics we fully understand if you want to put us 'on probation'.
As for the why part, we've decided that we'd rather make a bit less money in the sort term and be around in the long term as opposed to chasing you away or giving a competitor enough air-supply to make our lives miserable.
We sincerely apologize for our past behavior.
As another token of our newly found conscience we will create a board of 10,000 randomly selected users that get to vote on changes that will affect privacy in a negative way, the advice of this board will be binding on us. What with facebook now being larger than most countries we figure democracy is the best way forward. We're making this a sampled democracy rather than a representative one to limit the impact on the day-to-day dealings with our site, however if you want to you are always eligible to vote on any proposals the board votes on and your vote will count just as heavy as a board members.
This policy is effective immediately.".
That would win me over.