Passengers are happier when they have a good idea what they'll spend before they show up at the airport. SAS can charge a bit more, and still make people happy.
The lure of bag fees may be too much for JetBlue to resist, but it would take a big brand hit if it decides to do so. Coupled with the airline's new business class service, many passengers will wonder if the JetBlue they loved is gone forever.
Airlines have no trouble getting passengers to use Wi-Fi -- when it's offered for free. The brand benefits would be enormous if JetBlue kept it that way. Other airlines should consider doing likewise.
Onboard Wi-Fi isn't as simple as slapping on an antennae and charging to access the Internet. Airlines will need to develop smart models that give something away in order to make money from services people (of all ages) don't mind paying for.