Even if you think you're the best at something specific, you're not. Not because you don't possess the skills to be, but because you aren't professional enough to utilize the understated skill of humility. Anyone that lacks this, by definition, cannot be a coined as a "guru."
Take a look around Twitter. How many accounts do you stumble on that lists something like this as the user's description:
Social media guru and consultant that loves the Internet. I can help you get more followers and stand out online.
A truly professional SM consultant doesn't have to say what he is. In fact, he/she is usually the one that denies such classifications. That's because they don't need it. All of their work comes from the referrals they receive from satisfying all their clients. Every time.
Next time you run into a self-proclaimed "guru" in any industry, ask them for examples of their work. Better yet, ask them if the number of followers you have on Twitter means anything. Get back to me afterward and I'll tell you why they are wrong.
NOTE: This information is NOT coming from a "guru" of any kind.