In my honest opinion, I don't think it will be a good idea having a blog about bitcoin right now. Bitcoin is not yet on mainstream and you'll probably get less traffic than you expect. There are also lots of bitcoin blogs right now and you'll have some difficulty competing with them. I think running a faucet with good rates will be better than that.
Nope. Making a blog about bitcoin related topics is quite a good idea up to today even there are lots of blogs about that.
That will be his challenge. Compete with other bitcoin related blogs. So OP must think of a way to make his blog attract visitors.