Here's a little LBA story about the 50mm f4 macro I just bought yesterday.
I found the lens for an excellent price on Craigslist. I figured the seller either didn't know the value of what he had or really wanted to get rid of it quickly. He had excellent photos of the lens, however, as well as a good description of its characteristics. So I emailed him my interest. No response. A week later, the listing was still up, so I emailed him again. This time, I got a response.
Finally, I met up with him yesterday for the purchase. I asked him what kind of Pentax he used and he said that he didn't - he uses Nikon. I asked if he used the lens with an adapter, and he told me that a Pentax to Nikon adapter would require glass, which would reduce the IQ, so no. I asked why he bought it. His response: Because it looked interesting.
You don't really have LBA until you start buying lenses that you can't use. And, to justify my post in the M club, here are a few photos I snapped with my new lens, just to see if it worked.
And with my cheap teleconverter: