Sidewalk Etiquette

Sidewalk etiquette.  Is there such a thing?
Each morning when I get to work I must make a short walk from the parking lot to the entrance of my office building.  I would say that I am a moderately fast walker.  So, when I get stuck walking behind someone who, to me, is moving rather slowly, it can get aggravating.  At this time, I am faced with the question, "Is it wrong to pass someone on the sidewalk?" 

Now, I realize this may seem like a stupid question, but something about passing someone who is headed to the same place I am on a sidewalk big enough for only two seems rude.  Sometimes you might even have to step down off of the sidewalk onto the road to pass slower moving traffic.  This also seems awkward.  I realize that this is a petty thing to worry about, but I'd at least like to know that there are other people who think about things like this.

Of course, some people (one co-worker in particular) might tell you that I let things bother me too much.  For example, when going out for lunch with a co-worker I feel the need to ask everyone in the department if they would like to go as well.  It just seems like the polite thing to do.  Now, this results in the dilemma of those who would not like to go, but do want lunch brought back to them.  This is not necessarily a problem, but placing multiple orders, which then must be paid for separately, and catering to special requests (extra ice, light on the ice, etc.) can become semi-stressful.

Maybe one day I will be able to carelessly and quickly pass others on my way into work and run out to lunch without feeling obligated to ask if anyone else would like something, but until them then I will continue to contemplate the complexities of sidewalk etiquette and proper lunch practices.