That's a fun concept, but you might want to speed it up a little bit. I stopped at 20 because I got bored, it's way too slow. The ball moves too slowly and the paddles should shrink a bit faster. The change that occurs between 1 and 20 should probably happen between 1 and 5, or 1 and 3 instead.
Edit: oh wait, it's way more fun on Safari. On Firefox it feels slow and slugish, but on Safari it's great!
I think the game should scroll up infinitely as you progress. It will enhance the psychological feel of falling in space when the pong drops. And you can introduce levels, bosses, goals, etc.
The basic game play mechanic here is solid. Just like keeping a party balloon from hitting the ground!
Edit: oh wait, it's way more fun on Safari. On Firefox it feels slow and slugish, but on Safari it's great!