Barnes & Noble Inc. (BKS) announced Tuesday that it had adopted a so-called shareholder rights plan to ward off "efforts to obtain control of the Company that are inconsistent with the best interests of the Company and its stockholders."

The company didn't go into specifics, but it is likely a response to billionaire Ronald Burkle's recent disclosure that he had boosted his stake in the company to 17.8%. In a press release, Barnes & Noble disclosed how the rights work:

A few days after Mexican billionaire Carlos Slim reported an 18% stake in the company, Saks (NYSE: SKS) adopted a poison pill, disclosed in a filing with the SEC.

Under the terms of the "shareholder rights plan," if Carlos Slim or anyone else acquires a stake of 20% in the company, other shareholders will be able to acquire shares at half price. The company said that the plan will "impose a significant penalty upon any person or group which acquires beneficial ownership of 20% or more of the Company's outstanding common stock without the prior approval of the Board of Directors."

Shareholders should be appalled. Shares of Saks closed at $4 on Wednesday, down from a 52-week high of $22.19. In 1993, the stock traded north of $15 per share.

So shareholders should not be happy with any plan that gives the company's current management and directors more control over the future: Their track record is one of miserable failure. Given Mr. Slim's track record of creating enormous wealth, shareholders would likely be better off with whatever plan he has up his sleeve.

The Wall Street Journal reports (subscription required) that "Saks spokeswoman Julia Bentley declined to comment on the timing of the announcement, but said that Saks had a rights plan for more than a decade that expired in March 2008."

It must be illustrative to look at the returns that shareholders have received over that period.

It's pretty rare that you see analysts or shareholders (or anyone other than management) calling for stronger anti-takeover provisions at a company, but that's exactly what is happening at Sara Lee Corp. (NYSE: SLE). Chairman and CEO Brenda Barnes told analysts on the call that the company has "nothing structurally built in [to the company] that would prevent someone from coming in and offering a good price for the company" after shareholders voted to terminate the company's poison pill last year.

The company's turnaround efforts have been going well, and it's nice to see that Ms. Barnes is focused on building the company (and buying back shares as appropriate) rather than concocting plans to ward off a potential buyout.

I've never understood the need for takeover defenses. Here's the only takeover defense a company needs: If shareholders don't like the deal, they can vote against it. Artificial barriers (poison pills, blank-check preferred stock, shark repellent, etc.) to takeovers can do little other than discourage a potential buyer who might provide shareholders with a compelling offer.