In context it's actually very true:
"There are a lot of wealthy, successful Americans who agree with me — because they want to give something back. They know they didn’t — look, if you’ve been successful, you didn’t get there on your own. You didn’t get there on your own. I’m always struck by people who think, well, it must be because I was just so smart. There are a lot of smart people out there. It must be because I worked harder than everybody else. Let me tell you something — there are a whole bunch of hardworking people out there. (Applause.)
If you were successful, somebody along the line gave you some help. There was a great teacher somewhere in your life. Somebody helped to create this unbelievable American system that we have that allowed you to thrive. Somebody invested in roads and bridges. If you’ve got a business — you didn’t build that. Somebody else made that happen. The Internet didn’t get invented on its own. Government research created the Internet so that all the companies could make money off the Internet.
The point is, is that when we succeed, we succeed because of our individual initiative, but also because we do things together. There are some things, just like fighting fires, we don’t do on our own. I mean, imagine if everybody had their own fire service. That would be a hard way to organize fighting fires.
So we say to ourselves, ever since the founding of this country, you know what, there are some things we do better together. That’s how we funded the GI Bill. That’s how we created the middle class. That’s how we built the Golden Gate Bridge or the Hoover Dam. That’s how we invented the Internet. That’s how we sent a man to the moon. We rise or fall together as one nation and as one people, and that’s the reason I’m running for President — because I still believe in that idea. You’re not on your own, we’re in this together."
http://www.factcheck.org/2012/07/you-didnt-build-that-uncut-and-unedited/