Time machine missing backups?

Yes, time machine missing backup folders/files has been asked before and gone unaswered. I can't touch those threads as a new, reputationless member. It's very dissapointing to discover missing folders and files from full time machine backups.

I look forward to answers on this. This is by far one of the most disappointing feeling about Apple and a well recommended way of backing up.

Imac(21.5-inch, Mid 2011)
Processor 2.5 Ghz Intel Core i5
Memory 8GB 1333 DDR3
Mac OS 10.7.5

Folder missing folders and files:

/Users/[user]/Library/Application Support/