The Standard & Poor's 500 index will be getting a slight makeover next week, when constituent IAC (NASDAQ:IACI) gets the boot after completing its breakup into five distinct companies. Mutual fund giant Invesco (NYSE:IVZ) will take its place -- a very odd choice, under the circumstances.

I understand the S&P's need to give IAC its walking papers. The split will create five much smaller entities than the large-cap S&P 500 gauge typically tracks. As a consolation prize, three of IAC's spinoffs will be incorporated into the S&P SmallCap 600, replacing Tronox, Ditech Networks (NASDAQ:DITC), and Downey Financial (NYSE:DSL).

My bewilderment comes from picking Invesco to take its place. Why are we replacing an Internet company in one of the few sectors thriving in this economy with one in the languishing financial-services sector?

True, Invesco isn't some default-teetering investment banker or subprime-lending disaster. It's a growing money-management heavy with $457.8 billion in assets under management. The index also doesn't necessarily replace a departing stock with one within its sector. When Bear Stearns got bailed out earlier this year, medical-robotics darling Intuitive Surgical (NASDAQ:ISRG) took its place.

You still have to go a long way to find the last Internet stock added to the index. Naturally, the stateside-centric S&P 500 will skirt the fast-growing dot-com plays abroad, but why is (NASDAQ:PCLN) -- with a market cap approaching $4 billion -- not on the list? If the index wanted to pack a little financial-services flavor into an Internet-based addition, why not go with the smaller Bankrate (NASDAQ:RATE)?

Congratulations, Invesco. You should have been inducted into the S&P 500 fraternity several quarters ago. You would have actually been a fetching replacement for Bear Stearns, Countrywide, or any of the index's other recent departures. But since IAC is leaving on its own terms, it's only right that an Internet stock take its place.

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Longtime Fool contributor Rick Munarriz has never been asked to join the S&P 500. He is a freelance contributor to IAC's Citysearch, but does not have a financial stake in IAC or in any of the other companies in this story. He is also part of the    Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.