Is direct linking not forbidden by amazon associates?

Hello,

i found, that a lot of amazon associates users promoting products by posting direct links in forums, chats and other websites.

Link example:

http://www.amazon.com/Sims-3-Late-Night-Mac/dp/B003WU3CDW/?tag=BLAHBLAH-20

(BLAHBLAH-20 - changed amazon associates tag to not existing (i guess )

Is it forbidden or not?