Starting on 11th January 2008, the penalty fare for non payment on London's Bus, Tube, DLR and London Overground services increased to £50 from the previous level of £20. Apparently the penalty is reduced to £25 if paid within three weeks. Conceptually this is similar to what happens to many parking tickets.
Spending in excess of £3,000 per year on my season ticket, I certainly have no problem with this increase in the penalty charge amount. What the tfl press release does not say, is how many people are actually fined, how many people are prosecuted and how much revenue is raised through the penalty fare system.