My own opinion on that...
I believe TOPS has sold mainly to military and police around the world. I also believe the only reason you don't hear about them online as much is because they don't have a web-based forum, etc. to interact with civilian customers. I've seen that, in today's knife market, having a forum can be good, but can be a double-edged sword -- the flame wars that can, and do, erupt, can be tedious. I'm guessing that they don't need one right now because business is good enough?
Since TOPS is a shop (not a factory), where the knives are mostly handmade, they are pretty darn busy cranking out knives left and right. If you look at their site, and look around, you'll see that a vast majority of TOPS military and police users are very satisfied with the performance. In fact, groups like SEAL TEAM 3 and others had a hand in directly R&D'ing blades -- not in a official "this is a SEAL knife" way, but operators were directly involved. Most of the designs were borne of direct requests by mil and police users. The owners and operators of TOPS are former SpecWar guys and SWAT guys. You got top custom knifemakers like Rob SImonich and Trace Rinaldi doing collaborations with TOPS -- and I don't think they'd put their reputations at stake for anything other than a great quality company. Their following is huge actually, just in a different market area than consumer. But they sell a heck of a lot of knives to consumers too, I'll bet.
Personally, I've beaten the crap out of TOPS knives and been very happy, in both wilderness and tactical environments.
Hope this helps!
~Brian.