An obvious advertising rule: to reach ur audience u need to relate to them. Common sense: to relate to them u have to speak their language. Yes when I say language I don't mean just Arabic or English or the beautiful language of that boot-shaped country. I mean the dialect, the vernacular, the lingo.
For the english language I guess its easier. Let alone that the ad industry is very much established in UK or the US but as a language they pretty much speak what they write. Yes they have their dialects and their slang words which, at least in the UK, weren't used in ads until the late 70's or 80's. Before that great copywriter came along and decided to break the boundaries the language used in British ads was the proper standard english spoken only by the elites of the society.
The Arabic language is very different in that sense. I dont know anyone that goes around speaking in the classical written Arabic - except the Arabic teachers we all came across in school who we have to give credit to for trying to teach us something. But unfortunately, we all speak our dialects which are not purely arabic- some english words, some indian, maybe some iranian all muddled up together.
I've seen an increase of ads in the region where the copy was in the vernacular. Two I can think of are our Ramadan specials "Yabeela" and "Nigooshi". Very noticable but they probably made more money for MTC as targets to forwarded jokes than themselves. The campaign that I liked to a certian extent was the for Villa Moda Kuwait a couple of years back that was plastered all over the streets of Kuwait. If i remember it correctly they were copy only ads with a plain backround. The copy was in the Kuwaiti dialect.
I love the Arabic language, the richest language there is but advertising is not literature its about connecting to the people and eventually selling. Dialectal ads connect more and hopefully sell more.
But this is just one opinion..