danger will robinson, danger ... LOL, I have worked for several companies that have adopted "tabs" Initially they were simple enough, managing a small amount of data, but often what happens is that other groups within a company get ahold of this paradigm and use it for everything.
I have seen companies try to use tabs in a purchase flow. Tabs should have limited usage. Limited to displaying small amounts of data that a user can toggle between. They should never be used if there is a larger process involved like purchasing a product. Most people don't understand that if you have an open flow, you need to account for saving of data, and maintaining the state, error messaging, etc. of a process while the user is off tabbing into other data. I don't mean to rant, but have had my share of headaches dealing with issues associated with tabs. Its important to have a very specific usage for tabs making sure that all stakeholders understand how problematic they can be if used incorrectly.
From a very basic heuristic standpoint, the user can lose focus, get lost in the site, or be unable to recover from a process if tabs are used with too much data or within a process that should be closed.