First, it was the whole startup craze; TechCrunch, VentureBeat, GigaOm, etc... Then being exposed to startup job adverts on LinkedIn and other career sites... All these media sources together guided my decisions.
That's not advertising at all - that's news and culture. There's no shadowy conspiracy paying techcrunch et al to talk about how great big cities are. Job adverts, the only advertising part of your post, don't sell a lifestyle generally either - it's just a list of what they want and what they offer.