As noted in this GigaOM story, with Chatter, the AppExchange, Force.com, and VMforce it looks like this CRM as a service company is looking to be more than just a sales tool. The article also suggests that this is more than just Salesforce.com grappling with its market perception, as others in enterprise software consider it a threat as well.
"Clearly it is seen as the quintessential SaaS company but out of necessity for continued growth, it has moved beyond this Chatter, the AppExchange, Force.com, VMforce are all examples of Salesforce.com wanting to be much more than a simple (or even complex) sales tool. Initially Force.com created a programming platform to allow Salesforce.com customers to significantly broaden the functionality of their applications while the AppExchange created a marketplace for developers to sell those applications. More recently Chatter has sought to broaden the impact of Salesforce.com by creating a social feature set while VMforce moves decidedly down the stack in an effort to offer a platform as a service."