A system can maintain C and A despite a partition as long as no requests need to cross the partition boundary. In practice this isn't something you can count on, and CA systems tend to have absolutely horrible failure modes when reality intrudes, but - unless we redefine "partition" to mean a partition that actually gets in your way - they're not strictly impossible.
If you've got no coordination then distributed systems are much easier. That's a good design goal, for sure, and distributed database designers spend a lot of time thinking about where they actually need coordination. On the other hand, a lot of very interesting applications - like high-availability ACID - require coordination.
Longer version (approx. four years old) here:
http://pl.atyp.us/wordpress/index.php/2010/10/when-partition...