Assume that you have a mark in a sports' logo. You hop on line to see what traffic is out there regarding your mark and find that someone 1,000 miles away is using your mark in commerce and making money at it. Trying to be the gentleman (or gentlewoman), you nicely pick up the phone, place a call and try to resolve the matter over the phone. You tell the infringer that you want to resolve the situation, might be amenable to license and hope to keep those pesky lawyers out of the situation. You get a couple of grunts of assent and a promise to call you back. Rather than the callback, you get a summons and complaint in the mail, demanding that you respond in Kansas or Alabama rather than in your home forum. You call your legal beagle who advises that you may very well be stuck there.
That is the opinion of the U.S. Supreme Court in the MedImmune Inc. v. Genentech Inc., 549 U.S. 118 (2007) case and we think it bad law. The other side has filed a declaratory action against you alleging a lively controversy between your two companies. The Supremes ruled that this is likely sufficient to allow the other side to proceed in their forum.
Why is it bad law? It encourages lawsuits (you should have pulled the trigger first) rather than working things out. We are loathe to tell people to write their member of Congress when the country is still recovering from recesses ion, but somewhere down the line, this one needs to be addressed. For the time being, you need to give thought to filing first, calling second. Not the best of public policies.