I have noticed a trend in all recent redesigns of Facebook and Twitter: layers.

The growth of the Internet is comparable to the growth of a city. When we run out of horizontal real estate, we begin to build upwards.

The new overlay tweet design:

The new Twitter profile overlay design:

The new Facebook photo overlay:

We can learn a lot about online UX design by studying the history of how urban buildings were built, and why — and which ones failed and which ones still stand.

After all, isn’t the the chat feature on Facebook, the equivalent of conference rooms in a building? Aren’t hotlinks within online content the equivalent of subways and taxis in a city?

As we begin to build upward in this online world, what will elevators translate into? And, will we need doormen?

Side note: It would be interesting to map out and track the altitudes of the Internet over time.

Will the Internet become a world full of skyscrapers?