Sometimes the funniest and most intriguing things are those that are also very direct, as in the recent duel between BMW and Audi. In Europe these two companies battle it out pretty frequently, but here in the US, they prefer to keep the ads focused on themselves for the most part.
However, Audi decided to break the rules. They started things off with this ad in Santa Monica, California, to brag about their fully redesigned A4 line, which is a direct competitor to BMW’s 3 series.

Of course BMW responded, declaring on the board across the street that there was no competition!

Now with a response, Audi could start having some fun. Figuring this was the perfect bratwurst for its fans, it took the campaign online to get a much larger return on its investment. Audi invited its social media followers to comment and reply to this challenge.
One of the submitted photoshopped boards was the following:

Based on the cool ideas submitted by its social media followers, Audi came up with the following ad:

Unfortunately, BMW did not respond.
Nevertheless, both car manufacturers found that an unusual marketing campaign that incorporated social media and billboards payed huge dividends for both companies without blowing the budget.