The 'standard' share icon for websites used to resemble the Google Android icon -- three dots connected by two lines. However, there was concern that that particular design was too closely associated with one company, ShareThis, and that it could potentially be trademarked. This led to the Open Share Icon, which was designed not to be encumbered in any way.
The Open Share Icon has some nice implied semantics -- it can be interpreted as one hand passing an object to another ("sharing"), but it also resembles an eye ("look at this"). While those meanings don't necessarily leap out at you, once you know them the design makes more sense than Apple's icons ("arrows will escape from any box you put them in") or the ShareThis/Android icon ("two of whatever these are won't talk to each other and have to communicate via a third party"), Windows 8 ("click here for something about particle physics or maybe roundabouts"), Windows 7 ("it's a badly-wrapped gift! it's a flowerpot! it's both at once!") or Android 2011 ("Heisenberg's Uncertainty Principle applies here").
Sadly, I think Apple's design will probably be the long-term winner, and Open Share will go the way of the Betamax.