These are the recent annual financial results of Microsoft (left) and Google (right). COGS, SG&A, and R&D expenditures are shown as a percentage of revenues for that year:

Notice something? Google's COGS (cost of goods sold) in 2008 are 40% of revenue, twice that of Microsoft. This is not surprising. Google needs to pay to keep all their servers powered up and for their bandwidth. Microsoft sells packaged software, and stamping CDs (or more likely licensing) is relatively cheap.
This difference will have a significant effect on Microsoft's bottom line if software services are indeed the future of the industry. As more of the company's revenues shift to services, net margins will shrink.
Microsoft is in a quandary: If they blindly try to copy Google's business model, they will grind down their profit margins. However, they can't ignore the shift to services. What they will need to do is to build a model that allows them to capture 20% higher margins in services compared to Google.
This (in theory) is achievable. If Microsoft were to offer equivalent product value in the form of services compared to packaged software, customers would save the equivalent costs of running their own data centers and IT departments. This should mean that they would be willing to pay a commensurately higher premium for Microsoft hosted services.
The real challenge is positioning. If Microsoft can successfully position their service offerings in comparison to existing packaged software products, the savings value should be clear. However, if Google or other competitors were to more quickly build offerings based on a lower-priced model (e.g. ad supported, or convince customers they can live with less functionality), Microsoft may be in a hard fight to get so-conditioned customers to pay a premium for their offerings.
While it's still anyone's game - hosted software from Google hasn't unseated Microsoft Office or Windows, yet - they have aggressively taken the lead in capturing mind (and market) share. Microsoft not only needs to respond, but they need to fundamentally change the game in order to win in the long term.