If you don't cloak your affiliate links properly you lose money simply by not giving your affiliate link URL the respect it deserves! You should think of your affiliate links as business assets and try to protect and maximize their potential.
By not cloaking your links you're making it easy for your readers to replace your affiliate id with their own and have you lose the commission. Affiliates who don't cloak their links usually lose up to %78 of their commissions.
How To Cloak And Protect Your Affiliate Links