In the past five years more and more people have been advocating abolishing the use of target="_blank". They reason that when people want to open a link in a separate instance they will do so manually (using the keyboard or right-clicking a link) and that doing this automatically will break their flow and get them lost.
I think this is sound advice, but mostly for more advanced users. In my experience novice users often don't know how to manually open a tab in a new browser and get annoyed by losing the context of the previous website by clicking a link (this especially applies to 'link hubs' such as articles and e-mail clients.
Of course there are various way to improve this situation, for example by informing the user with a tooltip ("This link will open in this window, press ctrl on your keyboard and click the link to open it in a new window") or making it a setting in your app/site.
How are you generally solving this?