Yelp co-founder Jeremy Stoppelman is on the defensive again. This time, Stoppleman stopped by reddit for an AMA (Ask Me Anything) question-and-answer session where he fielded questions from owners who accuse the social rating site of bad business practices.

"There has never been any amount of money you could pay us to manipulate reviews," Stoppelman said during the online discussion. "We do have an algorithm that highlights the most useful and reliable reviews on our site which is about 75 percent of contributed content."

Business owners have long accused Yelp of displaying mostly negative reviews on a business's Yelp page so that the owners will pay up in advertising dollars in order to have those bed reviews taken down.

In the AMA, Stoppelman -- also a former engineer at PayPal -- expanded on that issue and touched on a number of others. Here, we've pulled out the highlights from Stoppelman's answers.

Related: Yelp: We Won't Stand for Businesses That Pay for Fake Reviews

On Yelp's review policy and filtering algorithms:
Millions of businesses don't pay us a dime and have fantastic reviews (only 57,000 of the 20 million listed on Yelp pay us). As you browse around the site you'll see reviews on any popular place. Word-of-mouth amplified at no charge.

We have a review algorithm that filters approximately 25 percent of contributed content automatically. We started our work on this in 2005 as soon as the site took off to ensure that the reviews consumers were reading were as reliable as possible. This idea and technology is something our competitors are now mimicking (hi Googlers!)

On Yelp's efforts to combat fake reviews:
Certainly shady businesses or "reputation management" firms do sometimes try to buy reviews. However we are constantly pursuing them with our own undercover sting operations. When we find businesses guilty of trying to purchase reviews we warn consumers by posting a consumer alert on their page and revealing the evidence.

On what he learned at PayPal and how it informs his own management style:
Joining [Paypal] gave me invaluable experience both in coding and later engineering management. I also built an incredible network of colleagues and saw the entire company lifecycle from young promising startup to public co. I think if you can spend a few years at a fast grower with a great "promote from within" culture that's a good risk-reward balance.

On what has and hasn't changed at Yelp over the years:
I still spend a ton of time with product and engineering, we do seem to get a lot more press attention these days, but perhaps most fortunately I haven't had to invest a lot of time with Wall Street (if you pardon the pun) ... our CFO Rob Krolik handles most of that.

Related: Reviewers Compare Yelp to a 'Slave Ship' in Ridiculous Class-Action Lawsuit