i'd watch out for this a bit guys, some huge loopholes a few will fall in to:
1/ You can only order with a Visa card, annoying as hell for those who havent got one but you can get a visa prepaid card to use:
http://www.visa.co.uk/en/products/visa_prepaid.aspx
you can also pay by cheque, but you have to write a cheque to the full amount of your application and they will cash the lot and refund the difference from what you paid to what you actually owed later on
2/ If you apply for tickets and are successful they will take the money in the middle of may. They will take whatever you are successful in getting so if you want to hedge your bets for getting athletics tickets and go for a pair of £50 ones for every night you'll be looking at a bill of 100 per night that they will take the lot. So in the middle of may you have to make sure you have enough funds free to cover your entire application otherwise it won't go through, if you win less you'll only pay for what you're getting but I'm betting if you dont have the funds they wont just cancel one nights tickets. You won't find out what tickets you've got until June though.
3/ They say if you dont want them there's a resale website, this will be launched in 2012 so you will have at least 6 months without the money on the tickets you've bought.
Now for my opinions on this... point 1 is obsurd, the olympics are meant to leave a legacy and be available to everyone. I know anyone can get a prepaid visa card to get them but with point 2 in mind everyone will have to get one and load it with the full amount for their application just in case... it's a bit stupid really.
as for point 2, i agree their lottery is a good idea and a fair method, but people want to see it so will apply to every night, they should tell you what you've been allocated before they take the cash and let you opt out if you want to or at least give you advanced notice of how much money they will be takign from your account to let you get it right
Just a warning on the 2nd point really, don't want all you guys going overdrawn because you lucked out and won £10000 worth of tickets you don't actually want
on a lighter note, only in the british based olympics would this happen
BBC News - London 2012 countdown clock stops in Trafalgar Square