First, business name rights are not established, nor infringed, by the filing and publication of a fictitious business name registration. Nor does one obtain rights to a name by incorporating under than name or forming an LLC, and so on. Rights to use of a particular name for a business, and the concomitant right to prevent others from using it, come primarily from registering the name as a trademark. In addition, the user of a name may acquire some rights outside of the federal trademark process; for example, there is a common law duty to refrain from cheating, misleading and defrauding customers as to whom they are dealing with, and some state-law unfair competition laws.

Next, infringement cases often bring up the issue of likelihood of marketplace confusion. As an example, there are probably more than a dozen "Joe's Bar and Grill" in California, and the one in Redding is unlikely to be confused with the one in Bakersfield, so neither infringes on any rights of the other. However, an outfit calling itself "Pomona College Alumni Group" is very likely to be looked upon as having at least some official connection with Pomona College, and a suit based on either trademark (assuming they have one) or common-law or state statute unfair business practices, trademark, fraud, etc. principles is likely to succeed.

So, there are two questions to ask yourself. No. 1 is whether there is a strong possibility of confusion in the marketplace as to a possible connection (that doesn't actually exist) between the entities. No. 2 is whether the challenging entity has a strong claim to the name, either due to an actual trademark or service-mark registration, or, alternatively, to being well known.

Another factor worth mentioning is that being in similar businesses or selling similar products or services increases the opportunity for marketplace confusion. For example, suppose there are two companies called "Purple Passion, Inc." If one makes lipstick and the other makes eye liner, there is a high likelihood of confusion. If the second company makes, however, paint, there is less possibility of a consumer misidentification, even though both are products for making things look purple. Finally, if instead of paint, the second company makes Zinfandel, there is an even lesser chance of confusion.

If the other name is a registered or recognized trademark, then you may have exposure under federal laws. Contact me directly.