This is no longer the game I purchased!
If developers want to do this sort of thing they should include it in the terms and conditions at the time of purchase. If not then there should be a new version (TF3?) and make it clear the game will evolve - and not alter the game - This appears to be a money making scheme that has a captive audience of those who already bought the game. I was not happy when acheivements were introduced as they also were not in the game when I purchased it - but I put up with them. But this new addition is not welcome at all.
As someone else said - "I was a fan of Valve" But I also am not any longer and will not purchase anything else from Valve - in face give me my money back.

Finding things were not always part of the game.
In NZ there is a Consumer Guarentees Act and Fair Trading Act - I believe this change in program contrevens both acts and I may even consider hitting Steam up for a refund on this basis (they were the retailer I purchased the game from).