It's not that they don't want users to engage with the service, it's that they want as much control over that interaction as they can possibly get away with.
Cynically, the more garauntess they can give to the other three quadrants, the more money they can make from them.
More positively, things like requiring reply/retweet/follow buttons with embedded content encourages more interaction with the service.
If a (lazy) journalist makes up an article from collating a few tweets you're now encouraged to reply, retweet and interact with twitter right there rather than using the Facebook Connect comments system at the bottom of the page.
Their value to the other three quadrants is interactions. They're not stupid enough to intentionally reduce that, though one could argue they're not going about it the best way.
Cynically, the more garauntess they can give to the other three quadrants, the more money they can make from them.
More positively, things like requiring reply/retweet/follow buttons with embedded content encourages more interaction with the service.
If a (lazy) journalist makes up an article from collating a few tweets you're now encouraged to reply, retweet and interact with twitter right there rather than using the Facebook Connect comments system at the bottom of the page.
Their value to the other three quadrants is interactions. They're not stupid enough to intentionally reduce that, though one could argue they're not going about it the best way.