more mining companies would stabilize the price even more so more companies would be good I think especially if the mining companies are the sole sellers of the mined btc, I wouldn't want this to be a top down company but a bottom up company i.e. the workers get the best deal set the price even, a fully unionised workforce of miners who call the shots to the selling topman the topman makes a tiny fraction of profit. itd work much better than mr.x selling for 120 one day then mr.y selling for 180 then mr.z selling for 80 to undercut. if they all thought to sell at say 150 and enough miners joined the company then the price would be pretty stable at around 150 only if enough miners thought this way, they could however selfishly go solo and sell for 200 but in the long run they would only be harming themselves and the whole btc economy.