Due to the nature of bitcoins they are too speculative. It is really hard to trade using currency with so high level of volatility.

Sad to admit it, but bitcoin society need credible trusted organization, which would regulate the market of bitcoins. Some rich man could take on this responsibility, but it would be much better if it was an open non-profit organization with the Supervisory Board consisting of eminent people with a good reputation.

This organization will accept donations in fiat money and at least guarantees the minimum price on bitcoins. For example, if the organization took donations for the $ 1 million, it can guarantee a price not less than 1/7.5 = $ 0.13 per bitcoin.

I believe that it is possible to imagine a more subtle mechanisms, but they must be clear to all market participants.