The New York Times Paywall Returns

The New York Times is finally putting their paywall back up.
On NYTimes.com, you can view 20 articles each month at no charge (including slide shows, videos and other features). After 20 articles, we will ask you to become a digital subscriber, with full access to our site. On our smartphone and tablet apps, theĀ Top News section will remain free of charge. For access to all other sections within the apps, we will ask you to become a digital subscriber. ... Readers who come to Times articles through links from search, blogs and social media like Facebook and Twitter will be able to read those articles, even if they have reached their monthly reading limit. For some search engines, users will have a daily limit of free links to Times articles.
I understand how tough the newspaper business has become, but making content hard to read and access on the Internet has not been a successful business model for anyone yet. I'm sure NYTimes.com knows what they're doing, but these changes raise an awful lot of questions about what content is going to be available from which sources. If a friend emails me a link to a NYTimes.com story will I be able to read it? Will services such as Twitter have to be whitelisted to enable access to content via links? By biggest question, though, is "how will this affect Instapaper?" If I can't Instapaper content then I'm going to find similar content elsewhere. Prices and details are here.