The stats seem to indicate yes, people trust anonymous reviews and testimonials. Some great stats about social commerce (which this sort of is) are at Power Reviews' Social Commerce Stats page.
Eighty-three percent of online shoppers said they are interested in sharing information about their purchases with people they know, while 74 percent are influenced by the opinions of others in their decision to buy the product in the first place.
Manage Smarter - September 2009
From 12 statistics on Consumer Reviews
90% of online consumers trust recommendations from people they know; 70% trust unknown users, 27% trust experts, 14% trust advertising, 8% trust celebrities (Econsultancy, July 2009, Erik Qualman, Socialnomics)
In case that doesn't hit you like a bunch of bricks, I'll repeat; people reported trusting unknown users of a product more often than experts or, even worse celebrities. We like real people. I think part of this may be a result of so many "expert opinions" being integrated into advertising already though. You see an expert in an add and you know he's been paid.
Additionally here's some relevant tips on using testimonials in advertisements, which strongly encourages testimonials, noting:
1. Always use real testimonials instead of made-up ones. Even the most skilled copywriter can rarely
make up a testimonial that can match the sincerity and credibility of genuine words of praise from a real
customer or client.
If you ask a customer to give you a testimonial, and he or she says, "Sure, just write something and I'll
sign it," politely reply: "Gee, I appreciate that, but would you mind just giving me your opinions of our
product - in your own words?" Fabricated or self-authored testimonials (those written by the advertiser
or their copywriter) usually sound phony; genuine testimonials invariably have the ring of truth.
It's really hard to fake sincerity after all, so real reviews tend to have that real sound that resonates with people in a way marketing copy, even great marketing copy, just can't.