The main risks of unregistered trademarks are: that you infringe other registered trademarks, that your mark will be stolen and that it is unregistrable.
Main risks:
1. Thousands of trademarks are stolen or lost every year. If your trademark isn't registered, then it can be hijacked in some countries. First-to-use countries offer some level of protection for non-registered trademarks.
2. The main risk is that your trademark is similar to previously registered trademarks. In this case, you'll infringe these trademarks, which might provoke the owners to sue you. This is potentially dangerous and we recommend ordering a trademark search first.
3. You can be using an unregistrable trademark that is generic, insulting or descriptive and cannot be registered or protected. Not all trademarks can be registered. See this article.
4. These trademark are difficult to defend. Someone can start using a similar brand and it won't be effortless to stop him.
5. Unlike registered trademarks, unregistered trademarks, cannot be sold separately from the business in which they are used.
Questions about trademarks?
Questions about trademarks?