Of course, they revolutionized the way we watch television.

I wonder how this thread might look like 100 years from now

The most inspirational empire to me is the Mongol Empire. Genghis Khan is one of my favorite historical figures. However, this empire quickly fragmented, and its rulers did not manage to rule their khanates effectively.
The most expansive empire in the world's history is the British Empire. However, this empire is a colonial empire. And it didn't annex the colonies directly.
The Spanish Empire is a colonial empire like the British one. However, I prefer this empire because it completely removed the local kingdoms and controlled its territories more directly.
The Roman Empire is one of the greatest ancient empires; however, I don't like the form of its governments much. It was first a small kingdom, then a republic, and finally an empire. But, its emperors couldn't declare themselves monarchs explicitly; most of its dynasties were not so stable and blood-related as the Han dynasty of China, and sometimes there were simultaneously 4 Roman emperors.
The dynasties of China were more stable and well-organized. However, it was too Confucian and centralized.
The Mughal Empire was a great empire for a few centuries, but it saw a lot of bitter events when the royal family members slaughtered one another to gain the throne.
The Macedonian Empire was a large empire for a few years, but it couldn't last for a long time or absorb all its peoples.
The Habsburg Empires (Holy Roman Empire, Austrian Empire, and Austria-Hungary) didn't function well, and it always faced ethnic tensions.
The Incas and the Aztecs were the largest pre-Columbian empires, but they were too tribal.

Perhaps I would give the title "the world's greatest empire" to an empire in ancient Egypt, Persia, Ethiopia, or the Arab world. However, it would take me some more time to decide

british empire and roman are top 2.

mongols would be up there to. i think youneed othave size and stability in govt(decently run) to be considered greatest. i think romans and britain checks most of those boxes, maybe mongols too.

My working definition of "great" would be insofar how you answer the following question: What tangible and permanent positive effects did the empire have upon the world?

(Clearly, we are agreeing that no "empire" is perfect.)

Without providing any proof or evidence as I feel these are fairly self-evident, yet subjective...

#1 US Hegemony
#2 British Empire

Tied for #3
Persian Empire
Akkadian Empire

Tied for #4
Rome
Umayyad Caliphate
Ancient Egypt (collectively, though very loosely "empire" -ish)

Tied for #5 (these act like empires though they are not)
Roman Catholic Church
Islam

The former three kingdoms of Ghana, Mali, and Songhai in Western Africa would qualify as small empires.

China was (however fragmented) and currently is an Empire (with a recently crowned Emperor). In fact China is the most enduring empire in human history.

The Facebook Empire is gonna be in the top 3 of all time one hundred years from now.

This is very interesting. I like this in principle.

Tho, my assumption is that technology and fashion move fast enough that in 20 years folks will not be able to tell the difference between facebook and myspace.

Facebook already has 2.5 billion users. More than twice the population of India. More than China by 800 million.

Technology will continue to make national barriers fall. Transnations will be the de facto nations of the future. People care about their online friends even though they may not even know their next door neighbors.

What does this look like, in your vision?

How would this work?

More like transtribalism than transnationalism.

Tribe is defined as "a social division in a traditional society consisting of families or communities linked by social, economic, religious, or blood ties, with a common culture and dialect, typically having a recognized leader."

Facebook has created the platform for making non-geographic defined tribes a reality. The strength of these tribes will only get stronger because of communication and travel technology.

Nationalism is defined as "identification with one's own nation and support for its interests, especially to the exclusion or detriment of the interests of other nations." Nationalist extremists are buggy whip makers trying to prevent the spread of automobiles.

Hmmm...

Facebook itself doesn't maintain the social structure that keeps the roads paved, transportation networks working smoothly, water and electricity flowing to me and sewer flowing away. I don't see how Facebook (or similar virtual platforms) will replace (local) physical government, and therefore the notion that it will replace "national sentiment" seems like a stretch.

The rise of communication technology (perhaps: online sports betting?) has had no effect on how strongly folks support physically local sports teams and how much they "hate" the team from "somewhere else" even though you frequently see folks wearing jerseys or hats of teams 1000s of miles away as a fashion statement.

I also don't see how maximal tribalism leads to peaceful co-existence. In fact, I think historically, maximal tribalism has (always?) lead directly to the empowerment of the warrior class in essentially all cultures. Doesn't "virtual trans-tribalism" merely increase the physical footprint of maximal tribalism? Doesn't sitting in your bedroom only interacting with people who closely share your own views make things worse, not better, generally?

Ultimately, I think Facebook itself is always at the mercy of the fashion du jour, and probably wont be able to innovate fast enough to keep up.