Users of the popular google toolbar addon for IE, it would be very much in your best interests to have a read of this rather eye-opening article of which I've just discovered over at IceTeks today. Google plan to pull a rather sly and unexpected move in an upcoming update to the toolbar, adding their new "AutoLink" 'feature' which basically adds links and info on websites which you'd normally believe to be placed there by the webmasters choice. However, all content added to the layout of the website by this feature is in fact on the viewer's side due to the influence of the new Autolink feature. This in the long run will cause a lot more harm than good for reasons detailed in IceTek's well covered and thought out article.
A highly recommended read for all parties.
As you may have heard Google will be releasing a new feature in it's popular toolbar, for those who unfortunately still use Internet Explorer. This feature will modify the web site and add links at the click of a mouse. No, not on the server, but on the user's side. Not quite hacking, but basically the same results of a defacement. The typical user won't have a clue that the site being viewed is actually different then what the webmaster intended.
Let's say you are selling books through your online store and post the ISBN number, Google Autolinks will turn the ISBN number into a link...to Amazon! So instead of buying from you, it will be just as convenient, if more, for the user to buy by clicking on the link, or perhaps the user will click, not knowing you are not affiliated with Amazon and buy it there. There goes a customer. Depending on the knowledge of the customer and what just happened, the customer might think he/she was still buying from you by clicking that link. So even people who want to support your online store will actually be misdirected due to this "feature".