The company originated in 2005 and has raised several smaller rounds of capital in the past. They're not a startup anymore; they're a full-fledged business.
If they're still raising VC, I'd still qualify them as a startup.
Facebook just raised $1.5 billion on a reputed valuation of $50 billion.
At what point do you stop calling something a startup?
When they start offering a return on investment? Facebook is an odd case as they are quasi public, but typically I'd say to be a "real business" you should be making money not taking VC.