I once had an "potential investor" come in to see my top-secret project (I was much more paranoid in those days). She loved it and called me back two days later and asked to meet with me for breakfast. When I arrived, she was wearing a transparent shirt and no undergarments, which freaked me out a bit (not relavent to story, but weird nonetheless). Instead of discussing money, she told me, flat out, that unless I hire her to be the president of my company, she will put me out of business. She claimed to have six people from Sun's Java team ready to start copying my software. She said she'd go to the Demo conference that year (where I was going to be presenting on-stage) and would badmouth me to everyone in the audience to insure that no-one would talk to me about financing at the conference. Then she stopped and waited for my answer. I thought about it (<500ms) and told her that I would not be hiring her. She basically told me I should should shut down my company because she was going to make it her job to ruin us starting that afternoon. Well, needless to say, even with complete insight as to what I was doing, a (supposed) team of engineers on tap, and a plan to ruin me, she never shipped a product. But I wish she had because we ended-up "pivoting" a few months later and it was the pivoted product that took us to the finish line.<p>Generally, copying won't happen until something has momentum in the marketplace. If, for example, I heard about Groupon before it launched, I would have reacted by saying "How are you going to get a lot of local companies to participate? Are you going to hire a team of door-to-door salespeople? It just can't scale." And I, of course, would have been wrong.<p>As far as bookmarking+todo lists goes, I was prototyping that idea a few years ago, but scrapped it because I didn't see it getting the kind of traction needed to be successful (at that time). Perhaps I will be proven wrong again!