Interesting to note that most people I've met will barter over the number of options or compare competing offers by number of options... but rarely does anyone ask how many shares are outstanding.
According to this article (http://www.inc.com/articles/1999/11/15748.html), "investment banks will target an initial offering price of around $15."
If you take this as true, you don't necessarily need to know how many overall shares have been issued. It would all depend on what level of the startup you get in obviously.
Anyone can confirm that this is a usable ball-park number?
VCs always ask and they're constantly evaluating investments. Why do you think that the less-practiced should wing it?