I saw a good writeup from Dennis Crouch of Patently-O, an award-winning patent law blog. Professor Crouch's article talks about the key requirement for a trademark registration — the applied-for mark can't be likely to cause confusion with a previously-registered trademark. This is the same test juries must apply in trademark infringement cases.
Most courts use a 6- or 8-part test to determine whether confusion is likely. You may be surprised to learn that actual confusion is not required and is usually pretty far down the list.
In Professor Crouch's article, he discusses a recent case involving an application for the word TakeTEN, which is used for a hospital's 10-day inpatient "lifestyle shift" program (for things like tobacco use, diabetes, weight control, etc.). The application was rejected due to a likelihood of confusion with Take 10!, a registered trademark used to encourage kids to have 10-minute classroom intervals involving physical activity. The two marks appear below:
On appeal, the rejection was reversed because the trademark examiner didn't meet the required burden of substantial proof that the two marks were likely to be confused with one another. The appeals court found that the services were sufficiently different, even though both owners advertise on the Internet. Did the court get it right? Do you think these two uses are likely to be confused with one another?
Trademark law invariably involves judgment calls over whether two names or symbols are likely to be confused with one another, taking into account things like relevant markets; similarity in sight, sound, and meaning; industry significance of all or portions of the two marks; intent; instances of actual confusion; and the type of product and its conditions of purchase. These factors are discussed in perhaps my favorite trademark infringement case, Gaston's White River Resort v. Rush.
It's important to select a trademark lawyer with experience in both registration and infringement matters to assist you in the trademark procurement process — experience helps a lawyer predict what a trademark examiner or jury would do with any given case.