The miners mine and hold, other mine and sell.

Investors and speculators buy, hold and sell.

You can buy random items in auctions and through the forums.

What are the reasons for the bulk of the bitcoin transfers? I read an article underlying the "dark side" of the internet and TOR network, and they seem to point out that bitcoins are now nearly the exclusive currency for the online "black market" (Note, they are not saying bitcoins are exclusively used for black market transactions)

What have you used bitcoins for?

Miner
Investor
Black Market
Other - explain

Hi, I was wondering if I should quit my job and focus more on bitcoins? Because I think it might get me even richer without a job?  

It can depend on Rules and regulations of the particular country if bitcoin is not legal tender in country than it will difficult to survive with bitcoins.
If i am in the country where bitcoins is legal than i will accept bitcoins as regular salary.

But There will always risk involvement.
But also has chance to get more profit as we see price fluctuation in bitcoin value.