A good guideline in web design is the back button. This is a single user interface that almost all web users know how to use.
Thus, the only suitable place to use links that open new windows is in states that cannot be easily obtained using the back button.
A striking example of this is the links in the middle of the forms: 
If users click on the form, the "Back" button will not receive them in the state in which they were - with a partially filled form.
This does not mean that target="_blank links are the only or even a particularly good solution to this problem, but they are the only place where users expect them, and they can be really useful.
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