As a result, any share loss doesn't necessarily equate to a fall in sales and, indeed, the launch of iPhone 4S would suggest that's especially unlikely.
Nevertheless, while RIM has recently garnered much attention for BlackBerry's crumbling hand in the US market, figures from Millennial Media suggest iOS has actually wilted at a quicker pace during the last 12 months.
Trading places
The fact the 'demise' of both platforms has come as Android has ascended to the top is no coincidence.
Google's OS now holds a 56 percent share of the market according to ad impressions on Millennial's network the same figure it accounted for in September 2011, but up 19 percent year-on-year.
Apple on top?
Nonetheless, Android's rise is spread across multiple manufacturers.
Despite the jump, no one particular handset has been able to knock iPhone off the top of the tree since October 2010.
As a whole, Apple remains the largest manufacturer in the US smartphone market, with a 23.5 percent share down just 1.48 percentage points year-on-year.
You can read the full Mobile Mix report for October on Millennial Media's website.