CIO — That may be the most important question to ask in business today. Having a clear response to this simple-sounding but complex-to-answer question is essential to business success. It shapes your company’s mission, priorities and growth initiatives.

Yet customer confusion seems to be having an adverse impact on some of the most influential IT vendors in the market. In recent months, HP (HPQ), Cisco and Microsoft (MSFT) have all seen their market values dip for various reasons, many of which can be traced back to that simple customer question.

Serving two masters is very difficult, and these companies continue to split their focus between B2C and B2B work, with varying success. After a tough Q3, Cisco decided to trim down, shutter its Flip video camera business and recommit to its core networking areas. “We know what we have to do,” says CEO John Chambers. “We have a clear game plan.” Not so for HP and Microsoft, both intent on serving two markets. And both are being challenged to articulate a comprehensive value proposition across all their diverse lines of business.

Now, don’t get me wrong. Cisco, HP and Microsoft are very successful businesses with storied histories and enviable financial track records. But customers are fickle. If you want to be number one or number two in every market you serve, you’d better have a maniacal focus on the right customers. I can’t help but wonder: Have HP and Microsoft grown so large that they’ve lost the ability to serve their audiences at the depth and speed necessary to stay relevant in so many markets?

I ask this in light of the examples set by Apple (AAPL), Oracle (ORCL), IBM (IBM), SAP and EMC (EMC), all of which have a clear focus on serving a single market. Make no mistake, Apple executives are 100 percent focused on B2C sales. If their iPads or iPhones end up in the enterprise, swell. But they have scant interest in selling to and servicing the enterprise business sector. IBM sold its PC business years ago and clearly focuses on the B2B market, as do Oracle, SAP and EMC. These companies grow by going deeper, not broader.

As the competitive landscape gets more crowded, who ultimately dictates customer priorities? You do. So how much does a vendor’s split focus on B2B and B2C markets matter to you when you’re choosing a supplier? Write in and share your thoughts.

Michael Friedenberg is the president and CEO of CIO magazine's parent company, IDG Enterprise. Email him at mfriedenberg@cio.com.