Please don't. If I want to open a link in a new tab or window, I'll use the appropriate key and/or mouse magic to do so. If I click on a link without modifiers, I want to leave the current page, thank you very much.
I usually stop visiting sites that try to second guess me and fail at it.
The web has some usability quirks, but it's not that bad if webmasters would only learn to keep their hands off and stop screwing with my interaction affordances.
I usually stop visiting sites that try to second guess me and fail at it.