Reasons not to like Lojban

Lojban is difficult

Lojban has deliberately been made as different as possible from all other natural languages in the world. The vocabulary is unmemorable (all the about 1350 "basic words", gismu, have 5 letters, and most have little similarity with their English counterparts), and the grammar is really strrrrange. For each word you must not only remember the plain definition, but also the ideas the word relate (differing in numbers from 1 to 5). In addition, in order to be able to make short compound words, you have to memorize the 3-letter affixes, rafsi. Or else, you would be saying mitrypavycinsygletyprenu, when mitpavycinglepre would suffice.

Lojban text looks ugly

One of Lojban's primary goals is to be written the same way as it is spoken. To achieve this, punctuation marks which are not spoken, such as the comma, period, exclamation mark, question mark and quotes, do not exist in written Lojban. Instead, the period is used to indicate where Lojban's morphological rules impose an obligatory pause in the speech stream, and the apostrophe is used for the h-sound when it occurs between two vowels. (The latter was introduced for "paedagogical reasons", ie. to make it easier to explain why the h-sound isn't, morphologically, a consonant.)

An example of how Lojban text looks, and the same texts in some alternate (however little used) orthographies can be seen in my orthography text.

Lojban's speaker mass is small and scattered

Let's face it. Even the most daring estimates don't leave Lojban with much more than one hundred competent speakers. Additionally, there are no complete sets of teaching materials available in other languages than English. So people who learn new languages to communicate with more people will not benefit at all from learning Lojban.

On the other hand, Esperanto is not spoken by that many people, either. It is estimated that it has about as many speakers as Icelandic. So, people who learn Esperanto aren't doing it to enable themselves to communicate with more people. If you want to maximize your audience, stick with Mandarin Chinese, English or Spanish.

Lojban is bloated

The Loglan that was presented in Scientific American in 1960 had 112 cmavo, or "little operator words", as they were called that time. The most recent cmavo list, from 1994, has a total of 1085 entries. Although some of the entries in the list are compounds, it illustrates an alarming tendency in the development of Lojban: to make new words with meanings out of all the combinations of letters that the morphological rules permit (known as "filling up the cmavo space"). It is probable that many of them will rot away and perish from not being used, but still they are "in the dictionary", so to speak, so people could be tempted to use them in written works, not least in scientific ones (many of the cmavo are the spoken equivalents of mathematical signs).
Arnt Richard Johansen,