I can't think of a startup, but I can think of people like that. The first people that come to mind are the Mythbuster people. Very handy, very good at cranking out their ideas into meat-space - but my impression is that there is very very little critical thinking. This is probably in large part due to the demands of TV (You need cool gadgets and experiments - who cares if the experiment is poorly conceived when it looks cool?)

But a lot of hobbyists also fall in to that category: doing projects that have already been done, or ones where the solution isn't particularly intellectually exciting/innovative/stimulating but just mostly takes a bunch of time (ex: spending your weekend programming a PLD to control a stop light).

It's kinda hard to accuse these people of "doing" too much.. b/c doing is better than just sitting watching TV. But say instead of programming a stoplight all weekend you for instance read some textbooks and learning some higher level math, or read some blogs to get some inspiration, or read some scifi to get in a more creative mood - It gets kinda harder to make an objective comparison of which is "better".