Yeah !!
thats a pretty important thing. In a cyber world where we hardly ever get to meet / talk to each other. How does another human being gets to know you to the extent he/she needs to before running into a conclusion with the review written by you.
Its one of the most effective way to personify yourself in a impersonal world like Internet.
Hmm... dont tell me, this didnt happen to you. Didnt you ever run into a review, after reading which made you think hmm... somethings there, lemme check why theres little deviation in the opinion & you promptly check the profile page and :-) with ahh, now I know. Well, without much analogies, all I could say is, Profile is like something that makes you as You to the rest of the people on the site.
What to Include:
Little personal background, details could be socio economic, education and profession. That pretty much gives a reader, to understand, what they can formulate your image within themselves.
What to Avoid:
Finer Personal Details, which can be used by malicious users to harass you.