After Facebook (NASDAQ:FB) had a horrible experience going public last year, many investors swore that they'd never own the stock again. But thanks to the recent announcement that the social-media giant will become part of the S&P 500 index, millions of index investors will end up owning Facebook indirectly.

In the following video, Dan Caplinger, The Motley Fool's director of investment planning, goes through the reasons Facebook is becoming part of the S&P 500 and what it means for index investors. Dan notes that the move was quite predictable, with other indexes having already added the social-media company's shares a long time ago. Dan then goes into the things that investors in the SPDR S&P 500 (NYSEMKT:SPY), iShares S&P 500 (NYSEMKT:IVV), and Vanguard S&P 500 (NYSEMKT:VOO) will need to keep in mind in the days before and after Facebook's addition to the index on Dec. 20.

Fool contributor Dan Caplinger has no position in any stocks mentioned. The Motley Fool recommends and owns shares of Facebook. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.