I saw a discussion on SLUniverse about a number of regions closing without notice. The discussion centers on the closing of Beach Front. See: Beach Front Realty Closed?
It seems the land owners collected the month’s tier from tenants and then closed the regions. Correspondence with Linden Lab revealed the closing was ‘deliberate’. I suppose that means the region owner contacted the Lab and scheduled the closing. Not having seen the actual correspondence I cannot tell if the phrasing is nuanced spin that might indicate the Lab closed the owners regions for some reason.