This doesn't really affect me as I am permanently logged in on all my devices. On the rare occasion that I am forced to re-login my username and password are automatically saved so.I don't need to type them in or remember them. It's really not difficult or a hassle, and I suggest that some of you look into password managers to make the internet less stressful.
However, I do not agree with a forced login to view threads. The threads are MNs marketplace, what pulls people in, I know they said people are pulled to MN by their other content but I very much doubt that, I'd bet 99% of traffic comes via threads found in Google. A forced login is effectively stopping people from browsing before they buy.
We are all in here, being passionate on this thread because we found MN, got sucked in and joined up so we can post. Folk aren't going to get sucked in if they have to sign up first!
I have no problem for signing in to be a requirement of enhanced features such as bookmarks/poster highlighting/posting etc, but you have to have the basic functions available for "free" ie without a login.
I would be very interested to see the bounce rate once people hit the forced login - as a PP said, many (most?) people once they hit a page all/email harvester/advert you are required to watch will just click away and go elsewhere.
If you want to get peoples data then you need to provide them with a far superior service if they do, rather than kicking them off the site if they don't.