Just to clear up, the "rounded corners" thing referred to a design patent on the iPhone. Apple also had design patents on their icons, but I don't believe they ever sued Samsung over those. They did sue over the grid layout in iOS, but that was another patent.
Regardless, things are a little different with design patents. Specifically, individual elements of the design don't have to be new (such as 'rounded corners' or 'silver' or 'wood'), but the overal aesthetic impression, as a whole, needs to be new. Design patents are actually kind of narrow - Apple wasn't claiming every rounded corner, but a device with specific bezel size and dimension ratios, specific radii of curvature on the corners, color, button placement, etc. The quote about rounded corners actually comes from their response to the German court during litigation over the German version of the same patent, where they essentially said "our design is very specific, and there a number of ways that Samsung could change their device and not infringe: they could change the dimensions and make it taller or wider; they could move the button on the front to the side or make it off-center; they could slap a big honking 'Samsung' logo on the front; they could change the rounded corners to square; they could add a wrap-around bezel; etc." Essentially, the patent claimed a combination of features A+B+C+D+E and if any of those was missing, it wouldn't infringe... but the media then jumped on it as "Apple claims to have invented rounded corners."
As an aside, Samsung added a wrap-around bezel to their next version, the Galaxy Tab 10.1N, without anything else... it didn't infringe the patent, despite having the exact same rounded corners that people say Apple claimed to own. It's really not the individual elements, but the entire combination - the overall look and feel.
As a further aside, during the US litigation, the judge held up the Galaxy Tab and iPad and asked Samsung's lawyers to identify which was which. They couldn't. :/
It's true and a difficult situation... You have to file the patent before disclosing the idea in order to protect it, but at that point, you don't have any revenue to justify the expense, so it's a chicken vs. egg thing. But, at least with software-based inventions, the speed of development and reverse engineering means there really isn't a first-to-market advantage anymore that you can rely on for your competitive differentiator: you work for a year or two coming up with your new software, publish it without filing for patents and hoping copyright will protect you enough, and a few weeks later, there's a competitor product out there. You may have been hoping for six months of exclusivity in the market, but you'll be lucky to get six weeks... and the guys with the teams of reverse engineering programmers are also the guys who spend their money on marketing, so if you were relying on word-of-mouth to expand your market, they are going to appear to be the originators and you'll be the guy hopping on the bandwagon.
The patent system is a great target to point at as crushing small businesses or individual inventors, but it's really a problem endemic to capitalism as a whole: the reason you can't compete with Apple or Microsoft isn't just the fact that they have patents and you don't. It's also their massive development and manufacturing and marketing and fame and liquid capital and... etc., etc.