There seem to be conflicting answers on this question. The most relevant ones seem to be at least a year or two old, so I thought it would be worth re-asking this question.
My gut says it's ok, because there are plenty of sites out there that do this already. Every major retailer site usually has links to the manufacturer of whatever item they are selling. go to www.newegg.com and they have hundreds of links to the same site since they sell multiple items from the same brand.
Our site allows people to list a specific genre of items for sale (not porn - i'm just keeping it generic since I'm not trying to advertise) and on each item listing page, we have a link back to their website if they want. Our SEO guy is saying this is really bad and google is going to treat us as a link farm.
Some clients are only selling 1 to a handful of items, while a couple of our bigger clients have hundreds of items listed so will have hundreds of pages that link back to their site. I should also mention, there will be a handful of pages with the bigger clients where it may appear they have duplicate pages, because they will be selling 2 or 3 of the same item, and the only difference in the content of the page might just be a stock #. The majority of the pages though will have unique content.
So - will we be penalized in some way for having anywhere from a handful to a few hundred pages that all point to the same link? If we are penalized, what's the suggested way to handle this? We still want to give users the option to go to the clients site, and we would still like to give a link back to the clients site to help their own SE rankings.