Could you explain why you think mining companies will fail? Miners should always, on average, be profitable. If mining becomes unprofitable for some, those with a low profit margin will be forced out, but those with a safer profit margin will be able to stay in and make profits.
I believe mining is in an extended bubble. Mining companies will become forced out by ASIC and low-energy mining.
The majority of successful bitcoin companies are private and dont offer shares to the public they can buy.
A company that can raise money has the ability to be successful. Many large companies are public.
A lot of mining companies have ASIC upgrade paths if you look closely. NASTY for instance should be one of the first to receive them from bfl.
As for companies raising money most countries now have strict rules about public offerings which is unfortunate and means only high net worth individuals are eligible to invest. It sucks. If bitinstant listed on glbse for instance the SEC would massively fine them.