Welcome to the forum!
Ignorance fought!
Welcome to the forum. 
A friend of mine was on the look out for a TV. One was advertised for the same price it could be bought new. She got a bit over the top wondering what on earth the seller could be thinking. She ended up calling the advertiser to explain what second hand was all about - the person explained she’d bought it on the never never, it was only two years old and she’d paid much more than the price for a new one. Oh whatever 
I could imagine the ad the OP refers to going like this:
Housemate: Just chuck/donate all that junk will ya?
Housemate 2: But it’s all valuable - people will pay good money for it.
Housemate: Ok - prove it - put up an ad, I bet you a tupperware lid that if you get any replies they’ll be time wasters.
People seek penny profits not just on Craigslist. I know people that will drive 10 miles to save 2 cents per gallon at the pump. Also, many online sellers will list things for a penny plus $3.99 shipping on Amazon. Their actual profit might be as high as $1, so I suspect or would hope that they’re all large businesses that are capitalizing on volume. I rarely list anything online for less than $10 considering the time and potential hassle involved. And think twice about picking a penny off the street because your effective wage rate is less than minimum wage.
I actually know that guy. The entire concept started in a threat on another website, and after many hundreds of posts we finally convinced him to do a website. Got a book deal out of it! Cool dude.
I can’t be the only one who wants to hear the stories.
I would love to hear them.
Same here. Sounds like a cool sociological experiment.
OP, my first thought was that maybe this person is mentally slow or handicapped in some way. If you want to make right, maybe email them and suggest they do one post and list everything or group like items for lot sales.
Out of which group? M4M, M4W, W4M or W4W?
Me too!
Which ever ones were most interesting/which ever ones made you vow to never do that again.
Well, I have a tendency to be loquacious, so how about first if I just give a general breakdown of each type (emphasizing on the “notable” aspects - each group had its share of “nice” responses), and if you want me to expand on any of them, I will. Keep in mind, beyond the initial posts, I never replied to any of these emails.
Men replying to women: This was by far the creepiest. If you ever want to see a slew of random penises from the internet, make a W4M post. And, we’re not talking that some of the replies even had anything about the “encounter.” It was just “Hey, I have a dick. Wanna see? Doesn’t matter. Here it is!” Some of these guys were graphic, too - describing “me” and what they would do to me. A few were very specific about who they thought I was. I don’t know if they actually had a person in mind or if they were just describing some imaginary girl, but I definitely needed a cleansing shower.
Women replying to men: If I had to rate the four groups, this was by far the most “normal.” They rarely sent pictures, but instead would just provide more background as to where they were, and when, what they were wearing, who they thought I might be, etc. There was one girl who was one of the biggest gold-diggers I’ve encountered (and considering where I live, that’s saying something). Her post read like a classified ad, and she didn’t describe me as much as some of the cars in the parking lot of said Starbucks. Basically, if I didn’t drive one of the five cars she listed, she wasn’t interested. Also, wanted to know what I did, my salary, where I lived (both the part of town and what kind of home I had), etc. I almost wanted to ask for a picture, to see if her looks merited such demands.
Women replying to women: There’s a joke / stereotype about how lesbians are quick to “settle down.” These replies did not disappoint. While relatively normal in the responses I received, these also read like classified ads moreso than “hey, I think that your ad is about me.” As such, they tended to include pictures, but much more tasteful than any sent by men. In fact, I don’t think I received a single topless (or bottomless) photo. One (rather attractive, really) woman invited me on a trip to go camping the following weekend. Something seemed rather off about that, because I can’t imagine this girl would have problems getting dates, so I really fear for the person who chooses to go into the woods with someone they met, on-line, a week ago.
Men replying to men: This was probably the bread and butter. I have a lot of stories about this - including the fact that I knew some of the people who responded (even though I never told them). Received more pictures from this category than any other, but if I had to identify them by their face, I could maybe do so for half of them. Also a lot of “I’m not who you are looking for, but do you want to hook-up?” They said this to a total stranger, about whom they had no idea of anything with regard to age, appearance or anything else. My favorite was of a guy who replied with a chest picture, but he was wearing a shirt. So, basically, he sent a picture of a shirt. (This happens a lot, actually, in various apps and sites; it’s odd) I almost had the chance to play “cupid”, because there were two guys who posted that they were at a particular location at a particular time. They were thorough in their descriptions of both themselves and who they thought I was. After looking at the details, I swear that they were each posting thinking that I was the “other.” I wanted to try and set something up, but was unsure how to do so. I thought about telling them both to meet me at a particular location at a particular time, so they could run into each other, but when they both realized that neither sent the invitation, it might freak them out.
Romantic Comedy? Rats.
How about it starts off as if it was a romantic comedy, and about halfway through, you realize it is more in the “horror” genre. 
Despite my earlier post, I can help but laugh at this example of a Craigslist request for disguised weapons…
Awww that’s so sweet - I wish you could have a way to set them up too!