Rules when it comes to links from friends.
Grammar: Does it sound like that person wrote it
Context: Does this person usually send you links with one "suspicious" comment?
How to prevent: Always question links before you click.
As one who grew up with MSN messenger I can say that even the one you thought would avoid such bad links would eventually fall for one.
Just noticed, if you see the grammar of this post name, you could say Bluestar could have written a sentence like that