From what I've heard 3Dfx intends to close up shop. These are based on various rumors that I've picked up from former 3Dfx employees. We all know Dave (former 3Dfx employee) is temporarily out of work. The stock price is sitting at <$0.50 a share - before the announcement, the stock was at $3+/share. The stock market seems to be under the impression that they are quitting as well.
Ethernet I believe that you are mistaken. Perhaps you might be right, but it goes directly against information that I was told by people who were working there as recently as three weeks ago - and I'm inclined to believe them since they are closer to the source. I hope that 3Dfx stays in business, and I know that if I were a stockholder I would probably vote against the action they have taken.
As to what happened, I have heard that it was mostly due to mis-management (bad decisions on chipset like the Rush, the Banshee), and poor design management which resulted in product slips (Banshee, Voodoo3, Voodoo5), and some issues relating to the foundary and demand forecasting. In the high-tech business, only the memory and hard-disk businesses seem to be more intensely competitive than the video card market. Margins are low, and windows for products are tight. There's little room for management errors.