Swipe ideas from some of the best Facebook ads
There it is again - a testimonial that demonstrates social proof, rather than having to rely solely on marketing copy to sell a product (or in this case, a service).
Dropbox have given the testimonial a lot of surrounding space, which creates a lot of emphasis on it. Chances are you read the testimonial before the rest of the copy, which is just what they were trying to do.
The straight-to-the-point ad copy reinforces the testimonial. A simple but highly effective ad, even if I can't for the life of me work out what the fancy bag is trying to say.