There's no One True Definition of what it means to be fractal, but a lot of working mathematicians use the criterion that a space's Hausdorf dimension is not equal to its topological dimension. Oftentimes (but not always), the Hausdorf dimension will be fractional, which is where the word comes from. Self-similarity is an easy way to satisfy that requirement in a way that's easy to explain, but it's far from the only way.
The article posits that maybe advanced alien civilizations may be motivated to build larger (and hence harder to to detect) Dyson spheres for the efficiency gains. While that's a possibility, it's also possible that being harder to detect is an end unto itself for safety reasons.
> A common example to help explain sunk costs is the movie theater experience, where a person buys a ticket and, 20 minutes into the movie, she realizes that it is a horrible movie and it will only get worse.
Offtopic I know, but twice in my life I've walked out of a terrible movie at the theater within the first 30 minutes and gotten a refund from the manager. Don't think you have to sit through terrible movies!
Don't bother with the rest of the Ender Quartet. While they're not terrible, they don't hold a candle to Ender's Game. There's just better uses of your time (like any other book on this page).
If you have out-of-band connections with all your friends and you have friends who are willing to jump through weird, nerdy, technical hoops, what do you need Facebook for?