Wiki's are certainly common practice at startups as well as mature companies. There are plenty available, Mediawiki is very popular. The one we use at my office tracks user, date/time of edit, and keeps a full history so you can see who edited what when. But, we host it ourselves so we could easily modify it and back inject data if we wanted to 'spoof' something - so it probably wouldn't be effective in the court of law.
Biotech industry may be different, but from most of the web startups I know they have platforms to share information easily (wikis, Google docs, etc.) but the goal being to share information and make relevant information quickly available to team members I've never heard of anyone designing their wiki or system specifically for tracking IP type of things, and who thought up an idea... Typically in a startup environment everyone is busting their butt to make the startup succeed, not trolling the wiki for an idea they can steal and start another company.
But I guess if you are logging new formulas for pharmaceuticals or something like that you might be more conscious of such things.