According to CEO David Bailey of Spotnight, learning a language in just 17 days is a highly attainable goal–one that he claims to have reached. But others maintain that it might not be as easy as he suggests.
How Effective Is Rosetta Stone?

Although many language lovers might recognize Rosetta Stone by name, its controversial emphasis on software gimmicks over person-to-person instruction continues to inspire debate in the realm of education.
Language Uncensored: Slang and Its Place In Culture

Although it is often over-looked as an informal practice of the young and the uneducated, slang is an integral part of the evolution of language.