It's probably about as common as being a CTO/VP/Director level employee within the general population. Most HN users are likely individual contributors; this is because most <i>people</i> are individual contributors.<p>(I did know one VP at Google who read HN. Only one, though.)
The HN crowd self selects to people deeply interested in tech. For instance, there's many VC's and founders lurking or public in the comments section. Never seen that anywhere else.<p>I wouldn't think about it much. The population on here is more likely to be VC/founder/VP than other internet forums but 95% of those people still aren't on HN. Too small sample population