Unless you have a lot of ASICs, it's not profitable anymore.
If you mean business in terms of law, it depends on country you live in.

I have about 219 GH and I run it as a small business. On my 2012 taxes in the USA I simply reported the fiat currency and goods that I received as misc income. Kind of in the same way that one would report gambling winnings. I reported my gear, deprecation and power usage as a business expenses.

I have various streams of income under a LLC and try to keep the various expenses that are associated w/ the income classified as divisions of the company in Quick-book's.

I plan on holding on to most of my Bitcoin's as long term investments. I have also purchased Litecoin's w/ my Bitcoins's and expect them to appreciate in value (unlike fiat currency).

As far as financial planning is concerned I consider my Bitcoin paper wallets as emergency savings. I am not a rich man in the financial $ense but I am debt free. :)

I would not be absolutely certain about it, and l guess the rules could be different for various countries and states.... but l guess it is how you run it.

I.E. l imagine it could be classed as a business and if you intend to make a profit it probably should be classed as a business.

But then again, depending on the laws in your region you may be able to class it as a hobby (but get more advice and don't take my word for it as l am really not 100% sure)

Cheers

It's a hobby. Unless you spend your full time resources on it and consider it your primary source of income.