Companies set aside stock for option pools, can issue more stock, etc. It's like the treasury/fed rolled into one, that governs company stock. For instance, the typical SV company will put 20% of the company towards employee option pools. SV is unique in setting aside a larger portion of the company towards employee ownership; companies in other sectors of the economy do not do this.

But I agree with your statement about companies putting the risk burden on employees and not much on themselves.