What are your thoughts on reciving PM's about sources?

I seem to be getting more and more of these just recently, for instance i had one yesterday that said 'have you used *******.com or can you recomend someone else, PM back or here is my direct email blah blah '

now it wasnt even someone i knew or even familiar with the username, so did not reply.

I just wondered what the general consensus is regarding this issue.