The European Union has eleven official languages, each one equal, and the European Commision in Brussels employs nearly 4000 people in its translation services, or 11% of its personnel, more than four times more people than even the United Nations. Large as it is now, this need will rise geometrically with the introduction of ten new countries (e.g. Poland and Hungary) whose languages come from entirely different families.
The required number of bilingual translators rises with the square of the number of languages. You may recognize this n2 phenomenon as a manifestation of the network effect. This force, combined with the increasing contact between formerly isolated peoples, is rapidly driving the bulk of the world's languages to extinction.
The obvious answer is to adopt a standard. It would not be a replacement of existing languages (for obvious cultural and nationalistic reasons), but an auxiliary second language. Like all good standards, this auxiliary language should be 1) simple, yet powerful 2) easy to learn 3) neutral, not favoring some parties over others. National languages fail all those tests. Numerous planned languages have been proposed, some quite interesting, but only one has "made it" as an international auxiliary. Esperanto is estimated to have 1-2 million speakers, which puts it in the top 3% of the world's languages. How to design an ideal language? You could start by cherry-picking the best features of existing ones. For example, Esperanto has borrowed (stolen, if you will) these features:
Next, you would make as few rules as possible, with no exceptions or irregularities. Esperanto has just 16 main rules, with no exceptions.
II. Does Esperanto Really Work?
Having studied with varying degrees of success six foreign languages from four language families (one non-Indo-European), I speak from personal experience when I say that Esperanto is incredibly easy. After only a few hours with a book, I could speak Esperanto nearly as well as Russian after four years of college study. That is perhaps not an entirely typical case (after Russian, anything seems easy, and I did already know some Spanish) but it gives you the idea.
Like some other planned languages, e.g. Modern Hebrew and American Sign Language, Esperanto enjoys a living culture commensurate with its size, complete with art, music, and literature, both original and translated. The language is used in four primary forums: local gatherings, the Passport Service, correspondence, and international gatherings. Each year the "Pasporta Servo"publishes a directory with the addresses of Esperantists willing to provide you with food and lodging, asking only that you speak Esperanto with them. This year's book has 945 names in 76 countries. What most Esperantists work their calendars around are the many international festivals, each typically lasting a week.
No Soul -- Languages don't have soul, cultures do, and the Esperanto culture is at least as vibrant as the suburb I grew up in. Any language seems mechanical when you are learning it, because you have to consciously think about the rules. Esperanto lets you get past this stage quickly.
No Poetry -- There is, same as in any language, and humor too, depending on the speaker. In fact, the flexibility of the language offers Esperantists freedom for word play beyond what many other languages allow. You can argue about the relative suitability of Esperanto, French, German, Chinese, Telegu and Tagalog, but it's certainly hard to write poetry in a language you don't know.
No Culture -- According to the French, no one else has it either, so Esperanto is in good company. The usual response to this objection is to parade the long list of original books, plays, and music, and even a movie, The Incubus, starring William Shatner, and available at Amazon.com. There is also a huge amount of material translated into Esperanto; I translated one of my favorite songs, The Long Black Veil.
No Speakers -- Esperanto has more speakers than 95% of the world's languages, and only a linguistic chauvinist would say that those smaller cultures are somehow less worthy. This complaint is the usual catch-22 that standards face before adoption: why should I use it if no one else does? Fortunately, Esperanto is so easy (as languages go) that it will always exist, as it has now for over 100 years.
No Reason ("Why not English?") -- English has already made a lot of progress in becoming an auxiliary language, but it still a long way from being fully accepted, and a lot of people don't want it to succeed. Anyone who has spent any time abroad knows that English is by no means universally spoken, even in certain large, affluent European countries like the one I live in. Even in a "professional" envirnonment, I frequently must speak German. English is not an easy language if you try to get beyond the pidgin level, and spelling is anything but phonetic (e.g., how do you pronounce ghoti?).