It's ok, not polite, to save seats at smaller regionals. In 2011 at the st louis regional, there were under 30 teams, and the venue has held 45+ teams the past two years. So it was roomy

but at internationals, 100 teams in a space that holds maybe 60 at most. I understand if your team has 30-40 members while others have <20, but that still doesnt give you a right to reserve entire sections....