This only works up to a certain valuation and on a certain % ratio. Yahoo paid $1.1 billion for Tumblr and $70m personally to retain Karp. They probably couldn't have paid $1 billion for the company and $170m for Karp, for example, without permission from his shareholders. And even then, any shareholder could hold out, claim fraud and file a lawsuit.
In smaller startups, up to the low teens or maybe 20 million, it's true that there is less protection for common shareholders. Many deals are <50% payment to the shareholders and >50% payment to acquired and retained employees. But in most of these cases the primary value IS the team itself. In a case where you, as a shareholder (either employee or investor), felt there was real value in the assets, independent of the team, that was stolen away in an improper acqui-hire type deal, you could sue and cause all sorts of problems for everyone.
Of course the best rule is still and always has been to try to work for people whom you trust and stay far away from those you don't.
There are certain protections and more importantly, risk awareness & risk mitigation for investor-shareholders that employee-shareholders rarely have. They don't have the information. The savy or bargaining power to negotiate the specifics of their contracts. Etc. That doesn't mean the equity is worthless. It's a few steps up from a verbal commitment but it has the same caveat, you need to trust the person its coming from.
In smaller startups, up to the low teens or maybe 20 million, it's true that there is less protection for common shareholders. Many deals are <50% payment to the shareholders and >50% payment to acquired and retained employees. But in most of these cases the primary value IS the team itself. In a case where you, as a shareholder (either employee or investor), felt there was real value in the assets, independent of the team, that was stolen away in an improper acqui-hire type deal, you could sue and cause all sorts of problems for everyone.
Of course the best rule is still and always has been to try to work for people whom you trust and stay far away from those you don't.