Most standards, up until the turn of the century, were required by governments to have RAND licensing terms in order to prevent abuse of market power. That's Reasonable And Non-Discriminatory, so you could charge fees but couldn't mess with competitors.
Governments are now pushing for Open Standards which must be RAND-Z or RAND-RF. Z stands for Zero cost, RF for Royalty Free. These Open Standards make much more sense for software or services delivered at low or no cost via the web, or as Free or Open Source software.
I pretty much agree with you. While I can understand their decision to sell to Opera, at the same time, I feel that Opera will probably ruin Fastmail by trying to turn it into just another Hotmail/Yahoo Mail/Gmail competitor.
Then again, who knows? Maybe this will end up being awesome.
If you read Opera's statements, they are not going to change the service. It's going to keep running as it always has. They are just going to use the technology to build other stuff or something.
