I think a key issue here is: it isn't any of their business. I did not promise I would be around 24 hours a day, and they have no introspection into my life to know when something is normal behavior or not.
There are tons of people who do, though: my girlfriend, the people I hang out with at my office every day, and even a few "long term allies" (as it were) I've come to know only online (and talk with on IRC). Some (in fact, many) of these people even have access to my exact location at all times via Latitude.
But the people I meet at conferences, the people who follow me on Twitter, or even the people who lurk in IRC channels I'm in? It is simply not any of their business where I am or what I am doing, and it is absolutely silly for them to expect me to tell them how long I'm going to be gone.
