I personally think it's one of the most difficult types of sites to tackle as a developer, and takes a great deal of experience and responsibility.
It's not the greatest industry to work in, and can be a little sweatshoppy, but it's a decent stepping stone for bigger and better things.
My background is in design, which in this regard is a little different than what goes on behind the scenes to deliver [insert ambiguous video content here]. Porn is graphic, and masking around man's lower thunder is not something most people want to do unless they have to. That was the point of my desperation comment from a straight-male's perspective.
I head up the development group for one of the larger set of adult sites on the web and my LinkedIn profile shows explicitly who my employer is. Before I forgot to turn off "Looking for new opportunities" I was contacted by a couple of top 20 traffic sites and one very large consumer device company about management opportunities there. They cited specific details in my current position as to why they were contacting me.
As some others have said in their posts before we deal with extremely high traffic, low latency sites, we tend to have a lot of integration behind the scenes, we work with extensive traffic affiliation programs and we know exactly how much our downtime costs. We also probably pay more attention to web analytics than most shops do as well.
It tends to be a bit more chaotic that most of my other jobs but I figure it's preparing me quite well for the future and my next employer will reap the benefits of this experience.
Granted I also wouldn't want to work for a company that would be biased against a designer who did adult work, so for me personally, it makes sense. If you have hesitations, I would fully recommend passing on working in adult.
I would say this is quite good to have in ANY portofolio. And, if somebody disregards anybody with this experience only because it was a pr0n site... well, worse for them.
but. "desperate?" no, i don't agree with that. saying that working for a porn company is an act of desperation is part of a self-perpetuating cycle that keeps porn ghetto-ized.
Interesting tid-bit I learned from friends that have worked in the industry: supposedly most industry execs are in fact women running the show.
However, as ScottWhigham mentioned (and IMHO of course) there's something desperate about working on porn, and it's not something most businesses want to see in a portfolio. EVER. Therefore, you're just collecting a paycheck UNLESS you're committing to porn industry as a career (more power to you, no judgement here). Furthermore, I think my greater concern is not knowing where some of the porn originates from in regard to under age victims, etc... and that just bothers the heck out of me.