While I have (so far, knock on wood) not encountered the former, I am seeing a great deal of the latter. A query letter that reads something like this:
"My friend, Bob Head Up My Ass, the New York Times bestselling author of Your Advances Aren't Enough to Cover My Scotch Bills, had this to say about my new book "The Best Things Since Sliced Bread"...And then the writer proceeds to go on at length about what everyone else in the world may think of him, his writing or possibly even his essay writing in high school. Sometimes they even quote a relative or family member. I will point out that so far, the biggest offenders here are - once again - writers with MFAs. (Now, I am not knocking MFA programs. I know several great folks who have graduated from or who are currently attending excellent MFA programs as we speak [I'm pointing at you, Gwenda Bond, my bookish superhero!] But for some reason, the ratio of pomposity to query-writing increases when some MFA graduates write query letters. Need I point out that getting an MFA doesn't necessarily imbue one with common sense?)
Let me be very clear: I do not care what your friends think about your writing. I do not care what your professor thinks about your writing. I do not care what your grandmother thinks about your writing. I do not care what your fellow writers may think of your writing. Not unless one of those writers is a friend of mine, and someone whose opinion I trust implicitly. And in that case? I want to hear it directly from my writer friend, not from you. It's called a referral. And you'd better believe that I will stand up and take notice if I get one from a writer or an editor friend of mine. But otherwise? Keep the blurbs out of your query. There will be a time and a place for your professional writer friends to help you out: AFTER you've found an agent, when he or she is trying to put together a pitch to a publishing house.
But until that point? The only opinion I care about when I'm reading your writing is my own.