Well, of course nobody is pushing you. You're not made to buy at gunpoint... but that's not the point.
The point is: are the 80% of the marketplace sales in line with the spirit of what i still consider a community?
Of course my opinion on the matter is: NO.
Being a large format lens collector, and having a long experience in the field (call me a lens junkie, i'm in no way offended), i think i have a few good and motivated reasons for it.
I have about 600 Ebay feedbacks, considering that not all the sellers remember to issue a feedback, that multiple purchases done at the same time grant just a single feedback, and that the vast majority of those 600 feedbacks come from lens purchases, i guess i can consider myself as an experienced buyer.
All my A Star glasses, and most of my best MF Pentax lenses, come from a time when i owned a Sinclair, Internet was unheard of, and the first BBS were just starting their activity.
I bought lenses from private parties, from physical shops, from Internet stores, from photografica fairs/swap meets.... none from the marketplace.
I tried. Can't say that i didn't try hard

The few nice deals last a couple of minutes, after that the item is sold! I'm getting old... probably i don't react fast enough

Nevertheless, i'm still capable to score a few nice finds, every now and then. Even a few Buy It Now... but i must say that it's quite uncommon, and that something like 29 out of 30 purchases come from Ebay auctions..
While the large format ones are for the most part collector's item, the optics i buy for my digital Pentax cameras are for actual use, i like to try them all, extensively (if i have enough room in my bags).
If i'm looking for an uncommon lens, most of the times i try the marketplace as my first resource. I love this forum and i like to interact with people who love and appreciate their glasses as much as i do.
The fact that i couldn't bag any purchase speaks volume. I'm either extremely unlucky... or there is something wrong.
I've read all the answers to my OP, and i found many moot points.
- the true amateurs of this forum care about their stuff, so you can expect better than average conditions. Well, on all those Ebay purchases i had just a couple of bad experiences, NEVER with a lens. Most of the times the condition was better than expected
- you know what you buy, and you can be sure that the lens is in Pentax mount. The vast majority of the lenses sold on Ebay are not mislabeled, if one is, usually it's a godsend cause you are likely to buy it for almost nothing! A quick look at the bayonet tells the truth about the mount. If there is no picture of the back of the lens you can ask for one...
- on the marketplace the seller knows about his stuff. Actually i often see plenty of hype, which is something i don't like. If you need to learn about the pros and the cons of a lens, better resort to the immense number of resources available on the Internet. Better not ask the seller! I just found this pearl on the marketplace: we should run to buy overpriced 35mm lenses cause the Pentax full frame is going to be released. I am afraid it won't happen soon, if at all (for the extreme satisfaction of the fanboys who are happier with less than with more).
- it's easier to trust a fellow amateur than an obscure Ebay seller. This is weird: can't see why it would be better than the Paypal refund policy! The couple of times i stepped on a poo i had all my money back, it's hard to say that there is something better...
My opinion is based on facts. Subjective? yes, i agree... but they are facts, coming from a statistically relevant sample, cause i buy many lenses. That's simple. But let's forget all that, my point is another.
I love this forum, even if recently i'm reading too often expressions like "get a life", or similar phrases, in response to a user expressing a different opinion. That's common in other fora, but was virtually absent when i joined pentaxforums.com.
Though most posts are still very friendly, and there is a feeling of being part of a community. I like it so much that it makes me sad to find out that the community-driven mood i appreciate so much is so rare on the marketplace.
As always, YMMV. If you don't see it, then good for you. Different sensibilities are always welcomed.
Originally posted by crewl1
Perhaps.
Grab lens 173/300, (don't think you've picked that one up in while) and go outside and take some pictures.
Come back when you are in a better mood

Maybe that's the reason... i didn't photograph anything today, just yesterday, most of the afternoon.
Com'on!
That's exactly in the track of "get a life".
cheers
Paolo