Peeking in on them from time to time simply won't work – long-term monitoring is usually required, as their movement can be so subtle. Stop-motion cameras work well for this. One of the best techniques is to detect their movement indirectly, by periodically checking the amount of junk food packaging in their trash cans throughout a workday.

For example, two hundred years ago, you could talk face-to-face or send a letter. A hundred years ago, you could also send a telegraph. Twenty years ago, you could telephone the person. Ten years ago, you could email. And today, you can do all of the above plus text message, IM using one of ten different services, write on someone’s Facebook wall, comment on a blog post, send a Twitter message…

The problem is that everyone has their preferred method. “Email me,” someone with say. “Call me on my cell, not my work phone, if it is an emergency,” says someone else. “Why aren’t you on Twitter yet?” says some Twit-ter.