I didn't downvote, but possibly it's because you're suggesting people build webapps to compete with anti-virus firms, CAD/CAM vendors and a couple of hardware manufacturers.
Interesting, because I would bet that there will be a serious web app contender in the CAD sphere at some point. I'm not so sure the OP is off the mark here.
Maybe someday, but I just can't see a web app that could seriously compete with the likes of Adobe or Autodesk in the foreseeable future. While there are online services that provide some of the features found in applications like photoshop, they are hardly compelling enough to get any Adobe or Autodesk customer to jump ship. Same goes for the like of Siemens and Mastercam, but probably more so.
Trend did a pretty decent job with Housecall - I think that was mainly an ActiveX control? I don't know much about the AV industry, but their market (Windows PCs) is being challenged by mobile devices, tablets, *nix, Macs and browser-based systems.
Other operating systems can get viruses too. Windows has the most viruses pointed at it because most people use it. The Antivirus industry is not really being challenged.
