A Sun-sponsored Web survey conducted on SMBs located in Europe indicates that more small and medium-sized businesses are adopting open source software (OSS). Its sizeable sample of 637 companies should give a fairly accurate picture of OSS adoption beyond Europe. In a nutshell, the conclusion was that 54 percent of SMBs currently use OSS in some form.
I took a look at the report, "Open Source Barameter 2009," and it is clear to me that the OSS adoption percentage is more or less consistent all the way up to 250-499 employees mark. As such, we're not talking about some fluke here in which a bunch of very small companies end up inflating the figures artificially.
Of course, since the study was really intended to draw attention to MySQL, it does go on to show how a strong increase in the adoption of MySQL is expected. If this interests you, you might want to check out the actual survey here (free registration required).
According to this report by InfoWorld, which seemed to have access to a bit more information than was found in the PDF report alone:
Based on the above points, my take on the situation is that SMBs are open to the use of OSS, though it is not something they are deliberately going for. This is evidenced by the fact that Windows remains the top OS in use, with no inclination to deploy Linux in sight.
The good news for OSS advocates, though, is that SMBs are less averse to using OSS in mission-critical apps, though influence by system integrators or consultants could be the reason here. The latter could explain the fact that usage appears independent of company size.
I think it would be interesting to hear how SMBs are actually using OSS. Perhaps you could share with us some interesting - or mission-critical - deployments involving OSS in your SMB.
In the meantime, you might want to check out an earlier blog I wrote on The Promise and Pain of Open Source. See if you can agree or even identify with my take on some of the problems inherent to open source use.