What I expected to happen was...:
Flowing water with two adjacent source blocks and above another source block should make a new source block.

What actually happened was...:
Water does not create a source block when above another source block. This results in currents in oceans that are annoying to try to fix and makes it difficult to fill in lakes or pools that are more than one block deep.

Steps to Reproduce:
1. Dig a 3x3 hole two blocks deep
2. Fill the bottom with water
3. Place water on all sides of the top layer
4. Notice that water is still flowing towards the center

OR

1. Find a body of water that is more than one block deep
2. Take a bucket of water from the area that is more than one block deep
3. Notice that there are now currents flowing toward the block of water you took

NOTES:
Fixed and tested with MCP 7.19:

--- a/src/minecraft/net/minecraft/src/BlockFlowing.java
+++ b/src/minecraft/net/minecraft/src/BlockFlowing.java
@@ -93,7 +93,7 @@ public class BlockFlowing extends BlockFluid
                 {
                     var10 = 0;
                 }
-                else if (par1World.getBlockMaterial(par2, par3 - 1, par4) == this.blockMaterial && par1World.getBlockMetadata(par2, par3, par4) == 0)
+                else if (par1World.getBlockMaterial(par2, par3 - 1, par4) == this.blockMaterial && par1World.getBlockMetadata(par2, par3 - 1, par4) == 0)
                 {
                     var10 = 0;
                 }