What makes the Startup a startup?

That's a bit twisted ;), I think the founder is the one can tell if he finished starting up the venture or not. So if you plan big, it is either IPO or being acquired it will not be a startup, or if the founder wants to run his own business then once the business is established. But in the later case it is not a startup as we dream of ;)

Yes and no... Google succeeded as a startup by bringing a lot of innovative and disruptive ideas to the market. Of course, at the core, they had the talent, the ideas, the culture and the organization to go with it. And they came at a time that was favorable from a business context point of view, a general public acceptance, an investment environment, etc. However, many would agree, myself included, that Google is no longer a startup in the full sense of the word. Size wise, revenue wise, organization wise, age wise, and definitely culture wise, they are getting farther away from what a traditional startup. Granted, they still have the unlimited coffee and junk food and a foosball machine, but the business model and the internal organization of a startup is not really scalable and no longer sustainable for the company. Everything from putting procedures around hiring, promotions and project management to electing the types of projects that are being selected, to assigning resources to ideas, everything is getting (and has to continue to get) more structured if they want to keep continue scaling their efforts. And one can definitely "feel the difference" when on site--and I have personally visited their mountain view office in 2004, as well as multiple times later. That is not to say, however, that there are strict limits on how old or how big or how profitable a company needs to be to still be considered a startup...