[nostrademons]

This is basically what private equity does, and is otherwise known as a "hostile takeover". It's been done legitimately for decades - Warren Buffett's mentor Benjamin Graham made much of his money buying controlling interests in companies that are selling below book value, then forcing them to liquidate the company and return the money to shareholders.

The only protection that shareholders get is the market itself. If someone wants to perform a hostile takeover on a firm that's selling below book value, and the shareholders believe that the firm is worth more as a going concern, they should be able to convince a deep-pocketed investor to come in as a competing bidder and buy the remaining shares instead. Such an investor is called a "white knight" - examples include Kirk Kerkorian for GM or Warren Buffett for Salomon Brothers.

If the firm is not worth more as a going concern than under liquidation, it behooves the shareholders to see it liquidated.

(And in your particular example, where they pay $100M for an autograph instead of liquidating and returning the money to shareholders, that just invites a shareholder lawsuit for breach of fiduciary duty...)