The poison pill I was aware of - one company adopted a pill that basically said - if any single shareholder acquires 20% of outstanding shares, at that point the board may(may) authorize issuing extra shares to every other shareholder - so that let’s say, instead of 1M shares for the company, there would now be 1.8M. The value of the takeover artist’s 200,000 shares suddenly is almost half. IIRC, this company sold - with consent of the board - for several hundred million, so trying a hostile takeover could cost them say, $50M. (When Air Canada and Canadian Pacific were fighting over who gets who, Air Canada signed long-term commitments with some partners that would have been expensive to break, thereby reducing its value as a merger).
Note the difference between large shareholders and the board. The large shareholders may control the board, nominate and vote members onto the board - but the board itself is obligated to look out for *all *shareholders, even the minor ones. If they lose sight of this obligation, the SEC and class-action lawsuits are waiting to remind them of it. If you want to see what happens with boards, and are bored, read Barbarians at the Gate. The management of RJR-Nabisco thought they could pull a fast one - talk their tame board into letting them (management) buy out the company at $55 a share, since share prices were well below what they should be, the company was oozing money. they had good old boy board members with executive jet privileges and all sorts of perks. The board balked, said legally they had to go by the book, ask publicly for competing bids. KKR jumped in and started bidding the price up. When the dust settled - $108.
Also note the board may include executives, but the board is a separate entity from management. Management makes the decisions and approved day-to-day operations. The board approves these actions, budgets, general directions,etc. (or boots the CEO out).
Absolutely, the board may simply buy out the minority shareholders. Most takeovers involve a requirement to acquire a specific percentage of stock (say 66%, but 50%+1 works) If the buyout company reaches that goal, the board may declare they are going private, they are recalling all shares at “fair market value” and handing 100% ownership to the buyer. BUT - the whole process must be fair. One grumpy stockholder can’t stop the deal; but if there is a significant question about whether the offer is actually fair, the courts could tie up the deal for years. Or… the buying company may decide to keep running it as a partially owned subsidiary, and let the minority shareholders keep their shares. The danger is that the taken-over company’s management must be very careful not to give the new majority shareholders any special consideration at the expense of the shareholders. That is generally too much hassle, if the whole point was to make the company part of a bigger empire working together.
(Let’s say you’re a company that makes transmissions, or airbags, or tires. Ford acquires 60%. If you give too good a deal to Ford, or fail to chase other customers, the remaining 40% might figure you’re not working in their best interest as well - and sue.)