As per...
http://www.tfl.gov.uk/corporate/projectsandschemes/19976.aspx

---quote---
Contactless debit and credit cards are making life easier. You can
already use them to pay for things wherever you see the contactless
symbol - and towards the end of 2012, you'll be able to use them on
buses as well.
---/quote---

With contactless card payments supposedly coming to other TfL modes in 2013.

It is however four and a bit weeks until "the end of 2012", and I ain't
heard anything about this. Absolutely no point in rushing it and bodging
it of course, but just wondering if anyone else is any the wiser as to
progress on this?

(I wonder if bus capping would work from day one - perhaps not, if the
beginning of Oyster Pre-Pay aka PAYG is taken as an indication.)