Most of the affiliate I have spoken with will use some type of affiliate cloaking or URL masking to prevent the majority of this from happening. The visitor can mouse over your affiiliate links, but the software does not show the affiliate link in the browser bar, but shows a url you make up. In the case of the url cloaking, when a visitor clicks on your cloaked link and is forwarded to the affiliate offer page the url does not display your affiliate code, but a url you make up. Hope this helps.