It's a valid question, I often hesitate when adding new extension methods. When extending any types (ours or not) with common methods, I find having them in the same namespace makes it easier to reuse since they show up in IntelliSense and there's no extra `using` statement to remember. As for confusion or collision with .NET namespaces, in a way I find it's a benefit. Extending system types might be done to compensate for something the framework should already be doing. Adding it in their namespace means that it would be an as-is replacement should they decide to implement it in the future. It doesn't always apply, of course, so I personally see this as being on a case-by-case basis.