I can't count the ways when someone looked at some great new product and said something like, "I did something just like that 20 years ago as a PhD thesis", or comments like that.
"Visicalc, oh that was just like some mainframe financial modeling system I used on Mainframes..."
"Quicken, oh that's just a glorified spreadsheet..."
"Windows XP? Oh a total ripoff of the Mac, which in turn was a ripoff of the Star."
"Salesforce.com? Big deal, nothing more than Siebel running as an ASP"
"Oracle - gee we did that stuff in College in the seventies. Relational databases are just so last millenium."
I think comments like that totally miss the point. Yes, sometimes the kernel of an idea came from some other project. And often things are invented simultanuously in different domains. And ok, certain products 'perfect' what was done already in a more primitive way.
But I can salute and respect each of the products I gave as examples.
In my experience a 'successful' product has a relatively small bit of 'science' or 'invention' or 'creativity' and a ton of great engineering, not to mention marketing, sales and business strategy.
So there's nothing new under the sun, it's all just remixes. But that doesn't necessarily make it unimportant!