That context of size is important. To some people, 500 is a large company. Indeed, in many respects, 500 really is a large company. Only ~0.3% of US companies have more than 500 people [1]. But HP has 317,000 employees. So depending on who you are talking to, "large" suggests different things.
[1]: http://www.census.gov/econ/smallbus.html