Using a silk touch tool on webs doesn't drop the web as an item.
Comments 16
Using shears it drops string, but Seth says that it should drop cobweb item when you use Silk Touch.
Using a Silk Touch shovel on ice works, why wouldn't using a silk touch shovel on web? As far as I know, the shovel is not the correct tool for either material.
There is 3 "levels" of tool usage. "Correct tool", "Wrong tool" and "no tool". I think shovel don't work on webs because it is "no tools" catalog for webs. Sword count as "Wrong tool" so 2 uses, BUT there's no such thing as silk touch for sword (or shears for that matter!)
Would have to test it though.
If you use TMI's feature of enchanting,you can get Silk Touch on your sword and it would work but that would be cheating...
This is not a bug, but a feature request, please post it in http://www.minecraftforum.net/forum/1-suggestions/
I could be mistaken, but it seems that, that is intended. I seem to remember in the update notes that silk touch would specifically not work on spider webs.
All I could find is:
12w17a - Silk touch can now retrieve Ice blocks and glass panes.
No mentions of spider webs.