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If we go by the Chanos Rule, Netflix (NASDAQ:NFLX) shouldn't be here and Sirius XM Radio (NASDAQ:SIRI) is peaking. The rule -- coined a few years back by CNBC's Herb Greenberg as a nod to noted short-seller James Chanos -- refers to Chanos' theory that a company's growth peaks at between 25 million and 30 million units or subscribers. 

It's at that point where everyone who wants to buy a product or sign up for a premium service has done so. The only real growth at that point comes from purchases as either replacements or gifts. In short, the party's over.

There are plenty of examples, including the George Foreman Grill and LeapPad learning toy, that maxed out in that range. On the subscription front, it certainly seems as if HBO has hit a wall at nearly 30 million subscribers. The once iconic AOL service started to fade the moment it topped off at roughly 27 million accounts in 2002.

This brings us to Netflix, delivering streaming video to 43.2 million domestic users (and a whopping 69.2 million globally, but let's assume that Chanos was speaking solely of stateside potential) and Sirius XM Radio, which hit 29 million in total paid subscribers at the end of last month.  

Neither company is showing any signs of slowing, even though Netflix stock took a hit on weaker-than-expected stateside growth. Netflix expects to close out the year with 44.8 million domestic accounts. Sirius XM boosted its subscriber guidance on Thursday and is now forecasting to have 29.3 million members by the end of the year.

It will be harder to grow in the future. Netflix is already in 35% of the homes in the U.S., and it's hard to fathom half of the country on the same streaming video service. There are nearly 80 million cars with Sirius or XM receivers out there, and most of them may be dormant for a reason.

However, that isn't the only way we define growth. We've seen Netflix push out a pair of price increases since springtime of last year. Sirius XM expects to have receivers in 160 million cars in a few years, and even if the conversion rate on pre-owned cars is lower than new ones, the growth should still be incremental.

We've also seen a couple of products blow up the Chanos Rule since the term was originated. There were more than 30 million cumulative Keurig brewers sold before sales peaked earlier this year, and the iPhone continues to deepen its market penetration. Chanos has made a lot of money betting against companies, and Greenberg is one of the most brilliant minds in the realm of financial journalism, but it may be time to put the Chanos Rule to bed.

Stateside growth may be harder to come by for Netflix -- and Sirius XM -- but neither company is showing any signs of peaking in its market penetration. 

Rick Munarriz owns shares of Netflix. The Motley Fool owns shares of and recommends Netflix. Try any of our Foolish newsletter services free for 30 days. We Fools may not 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.