This study investigates the effect of Facebook on Arabic language attrition, i.e., decrease in language proficiency, as exhibited in the use of Colloquial instead of Standard Arabic, use of foreign words although Arabic equivalents exist, and committing spelling errors. A sample of Facebook posts and a corpus of spelling errors on Facebook were randomly selected and analyzed. Samples of college students and instructors were surveyed to find out the reasons for this new socio-linguistic phenomenon. It was found that most educated adult Facebook users use slang and Colloquial language. Some Arabic posts are fully Romanized rather than written in Arabic script. English words are transliterated and inserted in Arabic posts. Many adult Facebook users completely ignore Standard Arabic spelling rules. They spell words the way they pronounce them in their own dialects. Students do not seem to recognize word boundaries, cannot connect phonemes with the graphemes they represent and cannot distinguish vowel length. Students reported that it is easier for them to express themselves in slang and Colloquial Arabic. They feel they are conversing with others, not writing. Therefore, they write the way they speak and do not think about spelling and grammar. Results and recommendations are given in detail.