The survey of 200 SMBs carried out by SpamTitan Technologies found that all of them allowed internet access and some social networking applications in the workplace.
While 76.4% said web filtering was important, around half (49%) of all respondents admitted not using any filtering system.
According to SpamTitan, the two most common reasons given were cost and absence of any legal obligation.
SpamTitan says that the results also show that at least 50% of SMBs are taking positive steps when it comes to securing themselves against social networking attacks and around 16% of those that have not done anything yet are intending to do something in the next 12 months.
Ronan Kavanagh, SpamTitan's CEO, said that the survey shows that economic pressures and the pace of change in working practices have left many SMBs struggling to balance the benefits and risks of web 2.0.
"Evidently they understand the dangers and fully intend to protect themselves over time but this still leaves a significant window of opportunity for social networking attacks to leave key loggers and other types of malware on the network with potentially costly consequences", he said.
According to Kavanagh, social networking and Web 2.0 applications are second nature to young people entering the workplace.
They bring their Facebook, MySpace, YouTube identities to the office and at the same time use professional social networking for more work-related duties, he said.