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What exactly happens when a stock is delisted and sent to the OTC bulletin board? What about if the stock is relisted? Thanks, H.L.

Gregg Greenberg: It's not a great sign when a company you own is demoted from a major league exchange like the NYSE or Nasdaq to the over-the-counter bulletin board. It usually means the company is having financial or reporting troubles, neither of which is an encouraging sign for shareholders.

Nevertheless, just like in baseball, sometimes being sent down to the minors gives a player a chance to get his act together before returning to the bigs. For example, one of the best-performing stocks on any exchange last year was NutriSystem ( NTRI), which spent a brief time in Triple-A ball on the bulletin board before becoming an all-star performer on the Nasdaq.

Among other rules, the Nasdaq requires a company to maintain a minimum bid price of $1 per share. If a company's price closes for 30 consecutive business days below the minimum bid price, then the company is notified that it has 90 calendar days to meet the requirement or face delisting. The Nasdaq also will threaten a company with delisting if it doesn't provide timely financial reports to the Securities and Exchange Commission.

The NYSE has similar share-price standards for continued listings, as well as even stricter criteria for market capitalization and financial metrics.

If a company fails to meet these listing requirements and is booted off, then management may decide to trade their shares on the less-stringent over-the-counter bulletin board.

Unlike the Nasdaq, the OTCBB doesn't impose listing standards, provide automated trade executions or maintain relationships with quoted issuers.

So what does the OTCBB actually offer its 3,300 listed companies? By its own definition, the OTCBB is a regulated quotation service that displays real-time quotes, last-sale prices, and volume information in over-the-counter equity securities.

To remain eligible for quotation on the OTCBB, an issuer must remain current in its filings with the SEC or applicable regulatory authority, and, well, that's about it, which is why most financial advisers tell their clients to steer clear of bulletin board stocks.

If a company's fortunes change for the better while its shares are trading on the OTCBB, then it may try to get its shares relisted on one of the major exchanges. In order to make this big step back to the majors, however, it must once again pass all the initial listing requirements set by that exchange.

What are the potential benefits or pitfalls of buying the stock of company "A" when it owns 50% of company "B," instead of buying company "B" directly? Thanks, M.F.

Well, you could buy shares of publisher Washington Post ( WPO), which is 18% owned by Warren Buffett's Berkshire Hathaway ( BRK.A). Or you may choose to own Moody's ( MCO) or White Mountain Insurance Group ( WTM), which each have 16% of their shares controlled by Berkshire.

Or perhaps pick up a position in financial services providers American Express ( AXP) or Ameriprise Financial ( AMP), both of which are 12%-owned by Berkshire.

Or you could just buy shares in Berkshire itself, one of the best-performing stocks in the history of the market and managed by the world's most famous investor. (Probably, you'll pick up the "B" shares, since they go for just under $3,000 a share. The "A" shares currently change hands at closer to $90,000!)

Of course, not every company has Berkshire's impressive track record. But Berkshire is a good example of the positive aspects in buying the parent or holding company instead of investing directly in one of its holdings. Basically, you participate in the subsidiary's upside, plus you get diversification -- and maybe more upside -- from the parent's other businesses. (Since Berkshire does not own a controlling interest in the above businesses, it is not technically a parent/subsidiary relationship, but hopefully you get the point.)

On the other hand, by owning the parent company instead of its subsidiary, you may also be penalizing yourself by missing out on some serious gains if the unit sees more growth than the parent.

Shares of asset manager BlackRock ( BLK), for example, significantly outperformed its parent PNC Financial Services ( PNC) after PNC took a 70% stake in BlackRock in 1995.

The outperformance became even more acute this past February when BlackRock agreed to merge with Merrill Lynch's ( MER) money management division to form a new company with nearly $1 trillion in assets. PNC will maintain a 34% stake in the new company, but an investor would have been better off holding a piece of BlackRock than PNC.

The bottom line is that you need to do the same homework you would do when looking into investing in any stock and determine if you'd rather focus your money on one piece of a company or the whole shebang.