It seems that one of those alternative universes is one where Facebook bought Twitter. It seems that in 2008 Facebook saw the potential in Twitter and tried to snap it up for $500 million in Facebook stock for Twitter.
According to the Financial Times, the messaging site co-founder Biz Stone said Twitter wanted to become not just a popular site but a viable business, rather than be taken over by another company. So he told Facebook to go forth and multiply. As it turned out he was right and Twitter did a lot better on its own.
Facebook stock however is not the same thing as cash either at the time people were penning long dull treatises on how Facebook needed a better financial model.
They are still saying that about Twitter, which has not made a profit in four years but at least it has its options. It is currently valued at $3.7 billion dollars.
Still if Facebook had bought it, it is unlikely that it would have gone through that huge period of rapid growth. Its main financial power has been in business and less in social notworking. If it had been stuck to users of one social notworking site it would have died a death.
Still it does mean that in that alternative universe tweets would be a minor thing, but Biz Stone would have a few more readies.