Since I may be switching to another PS3 soon, I was wondering if when you transfer data from one PS3 to another, does that data also include downloaded DLC? I ask because there is some paid DLC along with pre-order DLC and a few downloaded games that I don't want to lose or have to pay for again. I also gave a few friends some of my downloads, meaning that I can't download something more than twice, right?
All your purchases and DLC are bound to your PSN account, not your console. If you deactivate your account on your old PS3 and activate it on your new one, you'll have access to exactly the same content (although you'll have to download it again unless you perform a backup/restore or direct transfer, which would also move any copy-protected saves you might have).
The exception to this is if you intend to keep your old console activated: You can have up to five PS3 bound to a single PSN-account, but (due to a policy change) any content purchased after November of last year will only be available on two consoles at any given time.
You may download any content you've ever activated (paid, promotional or free) as many times as you want, it will stay in your download list forever. (Source: I've had a PS3 since relase, and even though I've replaced my fat one with a slim, my download list still contains the very first DLC I ever bought)