Identity and other deep shit.

I've been watching David Mitchell's Soapbox for the majority of tonight. He described himself as a comedian, actor and writer.
A writer. What constitutes a writer? Do you have to write a screen-play or witty articles in an underground magazine to be a writer, or does composing random tweets every day make you one? In that case, the majority of the world are writers! Actually, no, all apart from illiterate people are. Not saying that everyone apart from illiterates have Twitter, no. I mean that seeing as Twitter has limited characters, some of the tweets are rather short. Actually, there are tweets often only consisting of one word.
My train of thought was that if a Tweet could make you a writer, there are plenty of school-children who write random sentences and/or essays every day.
Naturally, as an egotistical human being I started wondering: Am I a writer?
I enjoy spitting out random ideas or thoughts, often rants, on this website I'd like to think was my own.
I never saw myself as a writer. I always saw myself as a weird teenager (for some reason will always be a teenager in my head (yeah, that's not a good sign. Run for your life)) who never fit in anywhere, striving to do just that.
However, lately I've discovered the wonders of drama. Not "O woe is me, he doesn't love me"-drama (which I am an avid fan of, as you probably could imagine (I would like to point out the sarcasm in that, to make sure you are without a shadow of a doubt of this matter)), but Theatre-drama.
So naturally I started thinking of myself as an actor.
They say that in the world of drama (I'm guessing that goes well for both drama-queen-drama and theatre-drama) it's good to be a little weird, so that kind of just slid out of my concious identity frame. 
Now, however... Am I suddenly a writer too? Can you be too much? Isn't that rather egotistical, to take up too many of the identifiable "titles"?
When is it the point of ridiculous?
Say you're an actor. But you also like to play an instrument, write sonnets to the neighbours cat and collect stamps that you've discovered outside the post office dropped only by women with moustaches. Say you met someone new at a party, and they asked the thrilling question; "Who are you?"
Would you answer, "I'm an actor-musician-writer-philatelist with an unhealthy affection for my neighbours cat, women with moustaches and post offices" or the more sterile "actor, mate." with an obnoxiously proud sniff of the nose following?
I trailed off.
I guess I am a writer. A rather unimpressive writer with a fondness of parenthesis.