IANAL, but I can't see any killer legal problems here (unless, of course, you signed non-disclosure forms on any of the articles, or get too close to the original author's work.) What is proper is hard to say. What is considered proper varies from context to context. The net tends to be very loose.
This is generally the way most people write term papers, but would not be okay for a dissertation or work published in a reputable journal.
If you are blogging, I doubt you would see any legal problems unless you were mechanizing article jumbling or ended up somehow copying a great deal of the sentence structure in the works.
There is nothing that prevents sources from suing, especially when money and reputations are at stake. If the parties you cite feel you are doing them material harm, they might sue or send a cease and desist letter.
There have been some high profile suits against popular authors for essentially rephrasing works of others.
The line between research and plagiarism can be thin.
The mere fact that you are asking makes me worry that you are working on a project that is pushing the edges, in which case you probably should have real legal advice.
