This was about the same time period that companies started suing over "look and feel". One prominent example at the time was Lotus suing (I think) Paperback Software, and also Quarterdeck Software (Quatro Pro). So, when it appeared that the same was happening between Sea and PKware, many BBS operators (at least in the Midwest) dumped Arc for Zip almost overnight. What made it worse was that PKarc was significantly faster than Sea's arc, so it looked like "If you can't compete, then sue". Of course, a lot of the details were kept sealed while the court case was going on, and all people had to go by then was what leaked out.