I visit a lot of tech company websites. Just about the first thing I do is click their "Contact" link, so I'll know where to put them in my geographical heirarchy.

Not every company has a contact link. However, they may have a contact _page_, if I guess its URL, like "example.com/contact.html", "example.com/contact_us.aspx" or what have you.

Sometimes I can't find a way to contact them at all.

Only some of the companies provide their street address. Many don't provide an email address, only a contact form.

Just now I visited Aha!'s website; their contact page says "We are located in California". You know, I love California, I have many happy memories of Death Valley, Venice Beach, Santa Cruz and Banner Mountain, where I lived when I was but five years old.

WHERE IN CALIFORNIA?

If you're worried about potential employees showing up in person at your office, say because they might drop off hardcopy resumes, then get a Post Office box which is in the same city as your office.