Bach predicted that Linux-based handsets will fail the "quality" test and not gain traction in the market, adding that the number of Linux variants used on handsets--17 by his count--will be subject to pruning by cellular operators.
While most Linux handsets are low-end "feature phones" the OS has recently been making appearances on smartphones as well, including models from Sony Ericsson. Google's Android is also a Linux-based OS.
Some business customers are choosing these as part of a broader strategy of using open source software in their companies.
Bach predicted that carriers will reject some Linux mobile operating systems--he did not offer specific examples--because they complicate support issues. My guess is that Android will pick-up any slack this creates in the marketplace.
As for Bach's own mobile operating system, Windows Mobile has recently experienced up-and-down market share and is seen as vulnerable to competition from Android, iPhone, and BlackBerry devices that offer better feature sets.
Windows Mobile 7, the next generation of Microsoft mobile OS, isn't due until later this year or sometime in 2011, depending on the rumor you believe. This allows competitors time to widen their lead on Microsoft, worsening its outlook.
Bach said Microsoft would talk more about Windows Mobile 7 at the Mobile World Congress, to be held next month in Barcelona.
"I don't think we have some specific challenge outside of the fact that our (user) experience is very skewed towards business users, and it's not as modern as it needs to be," Bach said.
This means business users should expect more options in Windows Mobile handsets, though how much support Windows Mobile 7 will generate remains to be seen.
Bach, a longtime Microsoft exec who also oversees Xbox and Zune, made the statements during a presentation to financial analysts last week at CES.
"I think everybody would say, there are too many operating systems in the mobile world today," Bach said.
"I'm not talking about the smart phone world necessarily, but if you just look across the million, two million, or billion, two billion, feature phones sold today, I don't think there's an operator in the world that wouldn't tell you that it's a pain to support all the different operating systems they have.
"In particular the 17 versions of Linux they have on feature phones, all of which are a little quirky and a little different, require separate network certifications, network product support, and the like that goes along with that.
"I think some of the current systems will fall away. I don't think that will be because there's not room for another operating system. I think it's because their quality bar won't stack up. And they won't get the scale that they need."
Bach said Microsoft's job "is to make sure we get that scale," but refused to speculate on the number of mobile operating systems left standing after some future shake-out.
"I certainly think we're going to be in that list of companies that are successful and then maybe there will be a few others," he concluded.