Putting on the marketing hat...
It's quite possible that Mobile Fidelity Sound Lab has no rights to "MoFi," if that's a colloquialism that they never actually used (as in, printed on a product or used to describe a service.)
Which brings in a couple of important points:
1. If you have a long, cumbersome company or product name that people like to shorten (Federal Express/FedEx, for example), you must use the shortened name formally and provably in order to have any right to it.
2. Note the word, "use." This does not mean "register with the USPTO." It means, print it on a product. Put it in a brochure. Use it online and make sure you have an archive and records of when you first used it. You can certainly register the trademark as well--and, as a small manufacturer, raise flags to even smaller and more litigious manufacturers that you have money and would be a good target to sue, since they have been using the same term since 1958 on their garage-made stainless-steel toilet seat covers (or whatever.)
3. "Confusion" can be cut and dried--sound-alikes are a no-no, for example. This can easily cross industries. Do a sound-alike to Google making barbecues and see how fast they come knocking. Beyond that, "confusion" is determined in court. Can the typical person tell the difference between audio gear and audio software? Pay your lawyer $100K and roll the dice. The defendant does the same. The lawyers throw a small party. One of you loses. Don't know which.
Trademark stuff is a royal pain in the ass. If you're in doubt, do a quick search of the USPTO database. Then have a trademark lawyer verify it and give it their blessing. And then start using it. Don't register it, unless you want to bring a bunch of crazies out of the woodwork and have infinite time and money for spending in court.
