Texting certainly hasn't declined, it's increasing by leaps and bounds, it's just moved to other platforms - as the article (clumsily) mentions. What you're calling text is SMS and it was the only game in town 10-20 years ago. Now there's Twitter, FaceBook, iMessage, Google Voice, Skype, and all sorts of other alternatives, better in some ways. IOW, everyone just has lots of ways to "text" these days, not just SMS.
IMO texting, Twitter, etc. are all useful. If I need to have a conversation with someone, but not urgent, email is good. If I need to have a conversation with someone right away, a phone call. If I just want DW to stop at the ATM on the way home, I can text her - at 1/4th the cost of phone minutes. And if I want to see what's new with all my favorites (more websites than "friends"), Twitter is ideal. ie, I can see what's new at 40 online magazines in a minute or two (and read the articles that appeal to me), instead of looking at 40 sites individually - just one useful purpose.
A scam?
Late adopters are hilarious ('get off my lawn...')
I remember my (now 90 yo) Dad telling me the internet was useless. He acted like he invented it a few years later...