The early e-mail services could send messages only within their own walls (rather as Facebook's messaging does today). Instant-messaging, too, started closed, but is gradually opening up. In social networking, this inevitable evolution may just be beginning.
Illustration by David Symonds. Courtsey The Economist.
→ in joysome pursuit of interesting ideas, a frothy cappuccino & a good movie → market segment manager at IBM → (views expressed here are my own, not my employer's)