There has been a lot of speculation since it was announced this summer as to why Twitter was embedded so deeply into the new iOS5. Actually, the speculation hasn’t been about why Twitter was embedded. That’s easy: Twitter is a super-simple message system used by more than 300 million people. The real speculation isn’t why Twitter, but why not Facebook.

There shouldn’t be any surprise that the world’s number two mobile operating system is trying to integrate more social media. Social and mobile is <a href=””>the beast with two heads</a>. There is a reason the two have grown so fast side-by-side: they support and augment each other. So clearly, a mobile operating system would be smart to embrace this idea and partner up with a major social media platform. 

On the face of it (hahaha! I hate puns) Facebook would seem to be the obvious choice. It has more than 800 million users world-wide, half of whom visit the site in some capacity daily and tend to stay for extended periods of time. It has integrated games and numerous time-wasting, distracting engagement-based tools from third parties (one of whom IPO-ed last week). While its growth is slowing, it’s not because people aren’t using it anymore, but because it might be reaching market saturation. Every day, new kids turn 13 (or say they turned 13) and log in for the first time, but who isn’t using Facebook today who might consider it tomorrow?

So why Twitter? By all measures, Twitter is the runner-up. Fewer users, less time spent on the site (by a huge factor, because most people use Twitter via a client), etc. Between the two, who wouldn’t choose Facebook?

But Apple didn’t, and there are some very good reasons.

1) Facebook is a site, Twitter is a service. By many different measures, Facebook is trying to re-build the web inside itself. When you add links and videos to Facebook, Facebook tries to show them to your friends inside of Facebook. Its games work inside Facebook. The only ways to access Facebook is at or one of the mobile clients it built (there are a handful of third-party clients, but they existed only because Facebook was slow to launch fully-featured mobile clients). 

Twitter, on the other hand, would be perfectly happy if you never went to its site. It wants you to use a client, on your desktop, on your cellphone, your smartphone, your tablet, your TV–whatever. Twitter works because it’s simply creating connections between two people, not trying to get you to stick around its site and play WordsWithFarmWars.

2) Facebook is closed, Twitter is open. Look at the above point and see all the ways Facebook wants you to enter its garden and never ever leave. It doesn’t like to even admit that you might update your status on Twitter or Tumblr or Postulous. Facebook wants you to think about the internet as a function of Facebook. An example: Ask anyone who has tried to connect their Tumblr to Facebook so that posts to Tumblr get mirrored in Facebook. It’s a pain. It doesn’t tell you when it works. It breaks frequently without telling you. These apps are outside Facebook and Facebook treats them like third-cousins it dislikes.

Twitter connects to… everything. You can have Twitter updates sent to your phone from 1999! Twitter lets any client connect to its API, and has been raising the number of API calls per hour (so you can use it more and more). I can send any 140 characters through Twitter. Services will shrink URLs so I can actually send a lot more than just 140. And when people click on that link, they don’t stay in Twitter, they go to the link.

3) Facebook is a competitor, Twitter is agnostic.  While we don’t ever have the thought: Should I buy an iPhone or should I join Facebook, Apple and Facebook see each other as competitors for your attention. And as we enter the attention marketplace, your attention becomes a very valuable commodity. 

Twitter is like the electric company: it’s a service. It doesn’t care what you plug into the wall, so long as it abides by some basic technical standards. 

The best example highlighting the real difference between the two services is that this year, the Arab Spring movement embraced Twitter, not Facebook. And now, Apple has embraced Twitter, as well.

This serves to underline the difference between these two tools to marketers. I’ve heard too many people look at the two tools and treat them as if they were the same. They couldn’t be more different. Putting them under the same “social media” umbrella is like treating a Bugatti Veyron and Nissan Leaf the same because they’re both “cars.”

So consider them two very different things when plotting your social media strategy for the coming year. Otherwise, you won’t be getting real value out of either of them.