Betfair should,...

Set commission to 0% on all accounts affected by the race, for the next 3 months.

Set premium charge to 0% on all accounts which had bets voided on the race for 3 months.

Explain why they kept the site up when there was a vulnerability in the system yesterday.  What if it had happened again!

If they did the first two, much of the sting would be taken out of the wave of anger with Betfair.  Fair enough things went wrong, fair enough you can't take £23m off someone if they don't have it in their account.  But if Betfair at least gave some impression that they respected the pain that many people do feel at not being paid out £23m, especially when there are clear precedents of big price ricks being paid out, would not that be fantastic Public Relations? 

By setting commission to 0% for a while for the affected accounts, at least some positive gesture is made that Betfair are going to be quid pro quo, and are not going to keep on profiting when things go right, but welching when things go wrong. 

Its not good enough to have David Yu leaving with £11 million, and massive pay rises for senior executives, who have presided over a float which cost anyone who invested at the start hundreds of millions of pounds.  Betfair haven't yet realised they must start acting like they care about their customers to prosper in the long run.