When going into The End the obsidian pad (and three blocks above it) will regenerate everytime the user enters The End, this will provide an unlimited amount of obsidian. I have made a video on this bug here - http://www.youtube.com/watch?v=G3sIXg-AF0Q&noredirect=1
*What I expected to happen was when I renter The End, i would expect the pad to not regenerate.
*What actually happened was the pad would always regenerate, this would provide an unlimited amount of obsidian
Steps to Reproduce:
1. Enter the end
2. break the pad
3. leave the end through the portal
4. enter the end again
5. break the pad again
6. repeat from step 3
Linked issues
Comments

JL2579 did a video on this, they created an obsidian generator - http://www.youtube.com/watch?v=P19ZtLF_z3o
I don't think this is a bug, you would get a very small amount of obsidian for each pad and I don't think the JL machine works anymore.
The infinite obsidian thing is a bit OP. They always want you to have a spawn platform though, for obvious reasons. The only potential fix I could think of would be to have a sort of "endspawn" tag on the 100 blocks (the spawn pad and the other 3 25-block sections above that pad) that prevents blocks from being placed and destroyed in that area. This would also potentially enable people to move that spawn using mods, rather than having to build around it.
Nothing new. Obsidian has always been renewable. Nether portals has same thing.
I agree to Alexander Ryan sugestion. I think having obsidian with nether portal or end platform is a bit cheated.
I'm still unsure why this is such a problem because there is so many obsidian, or in least pre-obsidian in Netherland. There is effectively infinite ocean of lava there.
The pad should be bedrock or unmineable obsidian