When the reason you bought a stock no longer applies, you sell.

Knowing what I know today, I will sell ING Groep (NYSE: ING) out of the long-term Jubak Picks 50 portfolio on the annual revision of that portfolio in December. (By the rules of this portfolio, I only buy and sell stocks on the list once a year. It is supposed to be long term, you know.) If you’re following along at home, you don’t need to wait so long, of course. (You can find the complete Jubak Picks 50 Portfolio here.)

I bought ING on this relatively straightforward story: The Dutch banking and insurance giant was redeploying assets from its mature markets in Europe into growth markets in the developing economies of the world. That, I thought, made this a good stock to buy in order to participate in the higher growth of the developing economies of Asia and Latin America.

Well, a little problem called the US mortgage market crash interrupted this plan. ING had started up a very successful effort at gathering deposits via the Internet in the United States called ING Direct. By offering higher rates than local banks, ING Direct had gathered $75 billion in deposits by the middle of 2009.

The speed of that growth put ING in a bit of a bind. It was taking in deposits in the United States faster than it could deploy the capital in its own mortgage lending business. So to keep its deposits balanced with its loan assets, ING began t buy mortgage-backed securities. That portfolio grew to about $50 billion. And when the mortgage market blew up, so did that portfolio.

ING wound up needing a $15 billion injection of cash from the Dutch government in October 2008 and about $33 billion in government loan guarantees.

Now, in October 2009, regulators for the European Union are making ING pay the price for that government aid.

They are forcing ING to break up into two pieces, banking and insurance, and to sell off its insurance unit as well as its ING Direct business in the United States.

The move will reduce ING’s balance sheet by about 45%.

What will be left after the sale will be a predominantly European bank.

That may or may not be a good business, but it’s sure not the business I bought when I added ING to the Jubak Picks 50. Gone is the whole strategy—at least for the conceivable future—of moving assets from Europe to faster-growing markets and going after the growing middle class in Asia and Latin America who wanted banking and insurance products.

Maybe ING will come up with a new strategy that will fit in with the global trends in financial services that I described in my December 2008 book, The Jubak Picks. But right now, the stock sure doesn’t give me the exposure to the growing market for financial services in developing economies that I wanted for this long-term portfolio

And in the short-term, I expect that one or more of the seven companies that I named in my October 30 post “Who will replace the fallen? (Banks, that is)” will pick up much of the business that ING is being forced to drop.

Full disclosure: I own shares of ING in my personal portfolio. I will be selling them in December when I sell the stock out of the Jubak Picks 50.