If there is a gap between written and spoken English, then there is a chasm between written and spoken Arabic. Written Arabic has had centuries more time to develop than English; therefore the dialects of Arabic are far more different (and harder to comprehend for an Arabic speaker) than the different accents of English. Imagine if all French, Italian, Portuguese, and Spanish-speakers still wrote in modernized Latin. That basically seems to be the situation with Arabic today.
There appear to be multiple levels of "formalness" in Arabic; the language gradually goes from extremely formal to extremely casual. There is classical Arabic, the "holy" language of the Koran. There is Modern Standard Arabic, which is used for formal written occurrences (e.g. speeches). There is the somewhat formal Arabic used in formal spoken situations and between Arabic-speakers from different countries. Finally, there is the language of the street - the many mutually incomprehensible dialects of Arabic that most people use in daily life. Unlike English, there are grammatical differences between each of these styles of Arabic. Indeed, one could make the argument that the different dialects of Arabic actually constitute separate languages, except with the same written form.
During the Arab Revolutions, there were several fascinating examples of this system. Most speeches in Arabic seem to use Modern Standard Arabic, which is quite different from the language of the street. This is true both in pronunciation and grammar, unlike the case in English.
However, some dictators attempted to add a bit of local dialect when addressing the populace. Tunisian dictator Zine el-Abidine Ben Ali, instead of speaking in the formal Modern Standard Arabic (as is the norm), decided to speak in the Tunisian dialect. More recently Saif Al Islam Gaddafi (the son of Muammar Gaddafi), in a speech to the Libyan people, stated:
Today I will speak with you... without a written paper, or a written speech. (N)or even speak to you in the Classical (fuṣħā) Arabic language. Today I will speak with you in Libyan dialect, and address you directly, as an individual member of this Libyan people. And I will speak extempore. Even the ideas and the points are not prepared in advance. Because this is a speech from the heart and the mind.
On the other hand, it seems that - despite his words - Mr. Gaddafi's speech was mostly not in the Libyan dialect of Arabic, but rather the normal Modern Standard Arabic.
Not all dictators followed this route. Egyptian President Hosni Mubarak never used the Eygptian dialect in his speeches to the people, preferring the more formal standard Arabic.
Now, none of this probably had a significant effect on the Arab Revolutions. All the above dictators fell from power, despite their different approaches to speechifying. Other factors are far more important than the form of Arabic that a dictator decides to use when making a speech.
Nevertheless, the difference between written and spoken Arabic is still a fascinating topic to explore. Many English speakers (and probably speakers of other languages too) naively assume that all languages are like English. This is not in fact true. As the example of Arabic shows, English is far more standardized and less diverse than most currently prominent languages. Exploring the difference between English and other languages remains a fascinating subject.