The definition of a “geek” is changing over time, hence people are no longer agreeing on a definite meaning and taking geek definition as a controversial topic.
A geek, for me, is someone who is obsessed about something, and most importantly, turns this obsession into a tangible product or service. A nerd is obsessed as well, but not necessarily turns obsession into something. A nerd could fail, more often. A geek is more practical and successful.
You can’t be a geek if you’re just a heavy user or consumer, you can’t just consume something and call yourself a geek, yet you have to develop something, i.e. if someone is heavily using social media and social networking sites then he’s just a consumer or maybe an obsessed user, but not a social media geek, once he develops a successful related product or service then he might be a geek. Same goes for Art for example, if you’re obsessed about art, have a good taste and appreciate great art then your not an art-geek, if you develop or create art then you go as a geek.
I also think that we can never describe someone as just a geek, it has to be associated with a knowledge or skill, i.e. SEO-Geek, Science-Geek, Computer-Geek, Music-Geek, etc. Because you can’t be everything-geek unless you are Ibn Al-Nafis Yet for me if someone is described as a geek, with no association, then I consider it as a hardcore, quick and efficient developer, maybe because it’s more related to my field and developers or programmers usually get most of things done.
Get something done and successful then call your self something-geek.