Saving our bitcoin in your website is like to buy your mining contracts. If your machines are still profitable, we will continue to get profits. But if your business fails, do you still guarantee to pay out the money plus interests? I know fractional reserve is not enough to pay out all of the customers.
Remember that mining is not HaoBTC's only source of income - our CNY - BTC exchange is making strides.
We have been in the mining business for a long time, long before the company was established - if there is anyone in the market that still makes money, there is no reason that we do not.
Also, we pay our users interest not only because we can turn good profit by borrowing and investing, but also because we want the good will from the community, which we may eventually leverage when we release our new products - in a way, we give the money that we would have otherwise spent on advertisement to our users to buy their loyalty.
If I were you, I would not bet all my savings on a service in a foreign country run by a bunch of people who don't speak my own language, but will I try it? Sure, as long as it is an amount that I can afford to lose, which according to own standard, two month's income.
. 
That wiould be verys awesome guys!
