Armen, the basic assumption is that the candidate has expertise commensurate with the level being applied for. Basically, the progression within the current company will reflect in the current position held, and the salary. Scale of business really really matters only in positions where P&L responsibility exists. In most others, that will give an advantage due to the kind of challenges faced/solved, and insights gained.
Working on the world's largest system/deployment of any kind is obviously an advantage in most areas.
There are CxO level folks on the forum who will wax eloquent about the strategy aspect of hiring. For mundane things such as running the operation itself, folks like me can tell you folks with higher quality experience and the ability to absorb the lessons are prized because they can provide wisdom even though they might not actually realize it at that stage of their career. The 80-20 rule will ensure that most of your product teams are average folks while a few outstanding folks drive it to success. For service cos, the frameworks and metrics will drive service delivery and experience etc. is only required to improve productivity and related gains.
There are obviously more qualified folks to talk about hiring in the IT industry, but from my limited experience, the quality of candidates has been quite surprising. The best cos also end up hiring buffaloes, while some small setups appear to be able to hold on to the strong candidates. Basically, it all falls to chance! We have switched to hiring motivated freshers who are really into tech and do not pay much in comparison with the rest of the industry. It is easier to find and hold talent at that level. Most folks around 8-10 years are supposed to be TL or Junior Manger level and in reality, most struggle due to the quantum-oriented nature of our IT industry.