Bitcoin / Bitcoins / Crypto Currency

It is achieved by solving complex mathematical equations using computing power. When an equation is solved a block is released. The equations become exponentially more problematic to solve.

It's pretty ingenious stuff and I would be lying if I claimed to fully understand it. But I get the gist of it

On this, does anyone know if it's possible for there to come a point where the value increases to the point that mining becomes cheaper?

ie - is there something in the design to prevent this. (I realise if mining < buying then the price will come down.)