I'm often asked to make small, almost trivial changes to our clients' websites. One of these changes that grinds my gears is the frequent request to "Make this hyperlink open in a new tab/window."
This bothers me because it changes the default behavior of links and takes away the user's control over his or her browser. Default behavior of a link is to open in the current window. Now, every browser/system I know of provides the user with an action that can open a link in a new tab (for example, cmd + click on Mac will do this). Adding a
target="_blank" to a link robs the user of this ability.
Clients' reason that opening a link in a new tab will prevent a customer from leaving a site prematurely and not converting a sale. Shouldn't we have faith that our customers will stick around and buy products if they want to? One might even reason that removing the default behavior might be discomforting enough to turn away users.
My thoughts, don't selfishly change default behavior if you don't have to.
Here's a much better written article on the subject: http://css-tricks.com/use-target_blank/