Instagram, the vintage-style photo-sharing app is barely two years old. Add to that zero (yes zero) revenues and no apparent business plan, and what do you have? Easy. Easy, if you’re Mark Zuckerberg and Facebook that is. The $1billion acquisition may be sheer folly, it may also be a land grab against an upstart startup, or it may prove to be another stroke of genius by the 27-year-old grand-daddy of social media.