A common marketing tool is to offer free trials. The thinking goes that if I give you 30 days to start using my product, you'll discover how much you like it and want to pay. Or in the case of software, it's that once you get all of your data in, the switching costs will be higher than the cost I want to charge you.
These companies need to learn from Twitter.
You may remember a time — say 6 months ago — when most people you spoke to thought Twitter was completely worthless and didn't understand why anyone would waste their time. I'm sure some people still feel that way, but over time Twitter's usefulness has increased exponentially as more people are using it and figuring out better ways to leverage the technology.
If you're giving me a 30-day free trial, chances are you're not allowing me enough time to get past the phase of not fully understanding how it will benefit me. We're all pretty busy, and 30 days passes in what seems like about 5 minutes. When I consider things like CRM or project-management solutions, I know it's going to take me at least that long to even get up to speed.
This doesn't mean free trials should never be used, but creative marketers may need to think beyond the obvious. I'd probably not recommend using it for software — from my experience the free level that can be upgraded to premium is far more effective.