Not because it will solve all of the problems. (gratuitous and predictable posts predicting the idiocy of most humanity except for us omitted here for brevity.) But it is true that many people may click twice because they aren't sure if their clicks registered. If you warn them that there might be a delay, those people who can read will exhibit more patience.

You should still implement other technical solutions (several shown here will work nicely), but you can cut down on a lot of the problems with a simple message to your users. Some of them will see it and they are the ones who deserve to be helped the most anyway.

It's okay to abandon the "us and them" mentality that many programmers and developers exhibit. The people who use our stuff are really part of "us" too. Talk to them instead of trying to be incredibly tricky and saving them from themselves silently. (On the other hand, a safety net is a good idea. And a lot of people won't listen to you when you talk to them. But you take reasonable measures to protect this latter category and then don't worry about them too much.)

---v