We looked very heavily at Disqus for comments on a product I worked on that was released recently, and decided against it in favor of rolling our own commenting

We looked very heavily at Disqus for comments on a product I worked on that was released recently, and decided against it in favor of rolling our own commenting system. Ultimately, what it came down to was that we could build an equivalent system that met our needs for less than they wanted in a contract. I'm sure that there are things Disqus does that would show improvements over our homegrown commenting system, but ultimately it just wasn't worth it. A basic comment system just isn't that hard to write, and it's hard to imagine a scenario when added functionality in your product's comment system would justify paying for an external system but that functionality isn't important enough to justify building it yourself.