What I expected to happen was...:
Players to be able to place water buckets in the spawn area if the server doesn't have an op.
Increasing the spawn protection radius to increase the area in which players can NOT place water buckets.

What actually happened was...:
If there is no op (or spawn protection radius is lower than default) players can place blocks in spawn, but cannot place water buckets.
If the spawn protection radius is increased, players can still place water buckets but cannot place blocks.

Steps to Reproduce:
1. Get a bucket of water
2. /deop all ops
3. Find spawn
4. Place dirt or something to verify that spawn protection is actually disabled
5. Place water bucket
6. Water disappears immediately. Right clicking anywhere or relogging refills bucket.

OR

1. Find spawn
2. Set spawn radius to 50000
3. Get a bucket of water
4. /op dinnerbone
5. Move several chunks away from spawn
6. Place blocks to verify that spawn protection is enabled
7. Place bucket of water
8. Water is placed and does not disappear