However, I would always suggest that no, it often isn't really OK.
I think it is not necessarily OK because I think there can be a temptation, unless we have already submitted our work, to take on another's good ideas into our own work. We can put ourselves in the way of temptation.
Additionally, we also might lead another off course with our feedback, damaging their results.
I was always happy to discuss my approach to assignments and the route I had taken with my peers, but was careful not to get involved in the work itself. Also, I will happily ask non-studying colleagues, friends or family to proof my work for sense, grammar and formatting (not critique the content). I think there is dangerous ground when you proof another's work on the same course... it is a step too far for me.
While peer review can be powerful, it does raise a lot of confidentiality and expertise issues that careful treatment and consideration. We could open ourselves up to the temptation of tweaking our own work in retrospect: a dangerous place to be, academically-speaking. To be avoided at all costs, in case I turn out to be weak!
Not to mention that you are asking non-experts to review non-experts. You need to be very directed, clear and careful in doing this.
Too, there is another issue: that of our own learning. If others tell us the answer, we haven't had to sweat and dig in hard to work out the solution for ourselves. A quick and slick answer doesn't stick with us, long-term.
I suspect a better way of dealing with this is instead, when you are asked a question, to answer it with another question. Because it is only through bumbling our way through things that we usually come up with our own creative solution. Giving people the answer does not help learning. Showing people the process helps them. The whole fish and fishing metaphor.
Sam
- Reference: Ritchie, Anne Isabella Thackeray (1885). Mrs. Dymond. UK: Smith, Elder & Co