"And yes, the invention is every bit as obvious as you can imagine."
The standard defense against this type of claim-without-support is that if it were obvious, and given that there are _lots_ of eyeballs on the subject matter, and given that it is highly useful, then someone would have already done it. Therefore, since nobody has done it before, it was not obvious.
The "it's obvious" rant is almost universal when someone sees an idea that they (a) know is good, and (b) understand. As an inventor and generally creative type myself, I can't tell you how many times people will say that something is obvious once I have explained it clearly to them, even though had I not done so, they would never have made the same invention in their lifetime. The corollary is that there is a high probability that they will then believe that the idea was their own. I once showed a choreographer the ending to her dance with which she was struggling; after its first performance, someone congratulated her on her work, especially the ending, and she took full credit even though I was standing at her side at the time.