Email is Being Overtaken by Social Media for Communicating

Email usage rates are declining sharply among teens and young adults as email is increasingly supplanted by text messaging, including social media messaging, according to comScore's Digital Year in Review. The data suggests this is part of a broader downward trend cutting across most ages.
Overall Internet-based email usage declined 8% from 2009-2010, according to comScore; the decrease is especially noteworthy considering that the total U.S. Internet population grew 4.4% from 211.7 million to 221.0 million over the same period, according to figures released by eMarketer last year. There were even steeper drops among specific cohorts, with email use plummeting 59% among 12-17-year-olds and 18% among 25-34-year-olds. A smaller (but still substantial) drop was also seen among 45-54-year-olds, where email use dropped 12%. The only increase came among 54-64-year-olds, where email usage rose 22%, reflecting growing Internet adoption by this age group.
With email use declining, and online social networks booming, it's only reasonable to assume that social networks (and overlapping channels including mobile text messaging) are substituting for email to some degree. The real question is whether email is simply stuck in a long-term secular decline, which will see it dwindle indefinitely, or whether usage rates will stabilize at some point based on, say, life-stage patterns or professional context.
While social networks can handle all kinds of communication, including casual and business-related, email could hold on to its turf in business-related and official contexts where social networks are judged unsuitable for whatever reason. It's worth noting that regular "snail" mail still carries a large number of official, business-related information, despite the advent of a succession of alternate channels like the telegraph, telephone, the fax machine, and email -- and messages received through the mail still carry a certain weight which messages delivered over those other channels simply don't (at least to me).
Proceeding from this analogy, it doesn't seem beyond the realm of possibility that email could retain its usefulness as a marketing channel -- because a message delivered to the individual's email inbox continues to carry greater import than one received at their social network profile. Or maybe not: maybe social network messaging will become so ubiquitous that it functions as both a formal and informal medium, suitable for delivering all kinds of messages from all kinds of senders.