The most basic reason to do a comprehensive trademark search is to avoid trouble.
When you start a new business or a new brand you want to be completely sure that you will not have to change that name later. Changing business name or brand 12 months or more after launch is often a disaster.
To stay out of trouble you have to avoid what the law calls likelihood of confusion. You can read on the USPTO's (The US Patent and Trademark Office) website: "A complete search is one that will uncover all similar marks, not just those that are identical." http://www.uspto.gov/trademarks/process/search/
So you have to answer the question: Are there other similar trademarks, being used for similar or related goods or services?
To answer that question you should do a free comprehensive search at Markify.com (there are other trademark search engines but no one nearly as accurate that is also free, see report).
- Choose you primary market: US or Europe.
- Limit your search to 1-3 relevant classes (business categories)
- Go through the result list and make sure that none of the marks is both:
- Too similar and
- Do similar things
Depending on your result list, this can be a bit tricky, learn more. It’s often worth a good nights sleep to get a professional opinion from a trademark attorney.