The "Goal" blog in today's NY Times reports that the new Red Bull Arena in New Jersey will have an entry system where season ticket holders will pass through the turnstile in the same way that NJ Turnpike drivers pass through the toll booth (although probably not as often!). They will be issued a card that they can keep in their pockets and will be scanned as they pass.
The article says this technology is already in place in several English football stadiums. In England, the fans are used to restrictions on who can get tickets to events. Because of a history of fans from away teams fighting with the home fans, you can't just walk up and buy a ticket. And, you can't just resell your ticket. So this type of system is very workable for them.
Here in the US, season ticket holders for all sports are used to reselling their tickets, or giving them to friends, family and clients. In fact many businesses buy tickets for that reason (although probably not for MLS games!). It will be interesting to see if this type of technology will be workable with our frequent resale sports culture.