I worked on slides for my talk at the code-sharing session at AAS tomorrow. I am going to talk about ethical reasons to share your code, and then focus on costs and benefits. Among the costs, I think the biggest real cost is answering email and support requests. I think the most overblown cost is the risk of getting scooped. When have we ever seen someone get scooped because they shared their code? Usually code sharing is met with deafening indifference! Among the benefits, I think the biggest real benefit is the goodwill and visibility it creates in the community, which leads to citations, influence, and collaboration. Will post the slides tomorrow when they are done (but of course they are visible on github at all times in all stages of development, people!).