Excuse Me, You're In My Office. Office Etiquette When You Have No Office.

So, I'm sitting in my favorite coffeeshop and it's one of those days when I'm trying to get something done and I'm totally distracted by two women sitting next to me having an honest to god conversation about how many grocery stores they shop at.  I'm not trying to be judgemental but in a moment of smugness I give them a look.  Which one of them catches.
"I'm sorry,  we're in your office aren't we?"  Instantly, I feel bad,  it's a coffeeshop!  I don't own this place, it's not my office, and they can talk as loud as they want about the merits of different grocery stores all day if they want.  I feel like some kind of hobbit protecting my rock from other, more relaxed, people. 
"ummm.... yeah.... sort of..... but it's ok."  They look very apologetic.  I go back to my computer and hope they stop looking at me.
It's weird to me that people are now very aware that any given place could be someone's office.  That it's mainstream enough for casual coffee drinkers to mix with a location independent's conference calls and that they try to be semi respectful of each other.  Some places are impossible to work (Starbucks, I love you but you have way too much going on in there) and others are just filled with location indie's (Barrique's thank you for embracing us) and everyone has their own limit for how much outside noise they like / can take.
Are there any etiquette rules you observe or have come up with for common spaces and working?
Mine are:
Phone calls - Don't do them in a common space.  Go in your car or go outside.  Your clients don't want to hear barista background noise, coffee grinding, people talking, etc.  There are plenty of people who are going to see this as really unprofessional.  Even short calls that are being done for business should not be held in a common space.
Tables - Don't hog up a huge table if the place is packed.  If you are working in a place that has natural busy times, offer to share your table if it gets full.  On the flip side, don't be afraid to ask another person who is working to scoot over if they are hogging a whole table.
Plugs - share them.  If you can't plug in you can't really work.  If you see someone looking for a plug offer them a half hour or so.
Don't Get Territorial - Seriously, I have seen people almost get into it over a chair or table that they "usually work in".  Don't be 'that guy'.  No one likes 'that guy'.
Talking - Some people want to talk to everyone and some people just want to work.  Try to be sensitive to what it seems like a person is doing.  I've had to leave a place before because "I have a really tight deadline" didn't stop a chatterbox.  Other days, I have plenty of time to chat and I think it's generally pretty obvious but it's kind of like airplanes.  Every once in a while you get someone who really wants to talk.   It's ok to move seats.