I can't believe I am responding.
Howver, I have been reading page after page of this hopeless unsolvable thread, and I just HAVE to say that I am going to speak up on the side of the masses here.
Is sitting at a table with my little kids while my husband waits in line to order *rude*?  I, personally, don't think so.  I can see other people DO think it is rude, and if I am offending you by this practice, my apologies.
HOWEVER!  When I am on vacation, on my VERY EXPENSIVE vacation that I have scrimped and saved for, with three very hungry and tired children and a marginally cranky husband, and *we* have the ability to nab a table and sit our tired buttocks down at it while one of the adults goes to order, am I sorry about this?  Do I feel guilty?  Let me just say OH H*LL NO!  If you choose not to do this, your choice.  If you cannot do this for one reason or another, I am sorry for that.  If you didn't have the foresight to see how crowded the restaurant was and go somewhere else, YOUR choice.  Now, if I have finished eating, and see a family looking for a table, you bet I will get right up and offer them my spot.  If the table I have is bigger than what my family needs, you bet we will scrunch over and let someone share the table with us.  Without question.  If I see an elderly couple, or a pregnant lady, or a family with very tiny kids, or a handicapped person who cannot find a table, I would probably offer them my spot and go eat on a bench somewhere.
But if you are just Joe Q. Public and you are annoyed with me cause I happened to be lucky enough or plan ahead enough to grab a table for my family - sorry, no sympathies.  As Captain Jack would say - I don't give an a$$ rats how annoyed you are with me.  Next time it could just as easily be me how cannot get a table, and be that the case I will go find a nice shady bench somewhere to eat on, and remind myself to plan a little better next time.  Sometime you win, sometimes you lose, people, and part of being a grown-up person is realizing that the world DOES NOT revolve around you.  
I shall now leave this train wreck of a thread and go back to peacefully lurking elsewhere.