There are two different ways to treat Esperanto, both of which come up in the comments. One way is to take Esperanto seriously as a proposal for a world auxiliary language that people from all over the world can use for intercommunication if they didn't grow up speaking a common native language. This first way of treating Esperanto for discussion immediately runs into practical issues and real-world trade-offs. As the article kindly submitted here for our discussion notes, "Because, of course, the massive, trumpeting, stamping, ear-flapping, blanka elefanto in the room is… English; English; English; the English language; the widespread global adoption thereof." It is already well known that the plurality of daily use of English around the world is use of English as an "interlanguage," communicating among persons who are not all native speakers of English, including millions of conversations a day in English that don't include any native speakers of English.[1] I have personally overheard hundreds of conversations in English in multiple countries among people who didn't grow up speaking English, and English is of course the interlanguage of online discussion sites such as Hacker News. (I have also overheard, and participated in, many hundreds of conversations in Modern Standard Chinese that include no native speakers of that language, as Chinese is my most proficient second language.)

For practical value for a language learner, incentives matter. People respond to incentives in deciding which languages to learn, and how attentive to be to opportunities to learn languages. And more opportunity to learn, with more sound recordings to listen to and more texts to read, makes it easier to learn a language. The pervasiveness of English all over the world makes English an easy language to learn--I'm not kidding. Precisely because hundreds of millions of people use English every day as an "interlanguage," English is quite "fault tolerant," full of social conventions about how to get around people with a beginning command of the language communicating with one another, including officially adopted controlled vocabularies for occupations like seafaring.[2] (Again, Modern Standard Chinese is similar in that poorly pronounced Mandarin Chinese is an actual lingua franca in many parts of southern China.) English-language daily newspapers abound all over the world, English-language videos number in the millions on YouTube, many recorded by second-language speakers of English, and English-language books and advertisements make up the plurality of the world's books and advertisements.

Languages spread around the world mostly by people using them or not for practical purposes. The majority of the settlement of the interior of North America by Europeans was done by Europeans who were not native speakers of English. (For example, both of my maternal grandparents, both of whom were born in Great Plains states, grew up in German-speaking families and had all of their schooling in the German language.) The freedom of the United States included a freedom to speak whatever language people pleased. (Abraham Lincoln funded German-language newspapers to help his presidential campaign, and Theodore Roosevelt campaigned in English, German, and French, the three languages he knew from childhood, in various places in the United States.) English was the customary language of governance in the United States, and still is not official at the federal level, but mostly English won out in the world's third most populous country because it was a common language that immigrants from a variety of places could use to communicate with one another (as happened in my paternal ancestral line). The huge population base of native speakers of English (in the following generations) in the United States who still had family ties to other countries provides English with a great advantage in spreading around the world.

Another way to treat Esperanto is to take it as a hobby, an exploration of the characteristics of a constructed language. Many language hobbyists have explored Esperanto from that point of view,[3] as I have. For a hobby language, the main criterion is fun, and I do not judge anyone else's opinion about what is fun. I don't waste my time in online discussion debating whether coin collection or knitting is a better hobby, for example. To each their own in hobbies.

[1] https://en.wikipedia.org/wiki/English_language#English_as_a_...

[2] https://en.wikipedia.org/wiki/Seaspeak

[3] http://interlanguages.net/Esp.html

http://miresperanto.com/konkurentoj/not_my_favourite.htm

http://www.zompist.com/kitespo.html

http://jbr.me.uk/ranto/