I think someone may have tried to explain this before, but it did not occur to me to try it until now. As you know, the rewards site has removed the PSN e-Vouchers from the site, and it looks like they may not be coming back.
However, I used my PlayStation Sony Card to purchase two games, and filled out the two forms and mailed them in. I just got the bonus points and I am also getting the credit on my card.
I know it's not as convenient as the e-vouchers, but at least this gives you a faster way to buy games from PSN (rather than buying a PSN card from a retail store and filling out the forms for it). You can download the games, and fill out the forms to get the 5x bonus points and a credit (if you choose).
Keep in mind that the purchase has to be over $10 to apply for the bonus points (I had a Sony rep tell me this before). So I suggest that if you are buying a game that's $9.99, that you buy more than one.
One difference for the digital downloads; when you fill out the forms, for the UPC code, I just put zero (since it's a digital download). For the item number, I got the long alpha-numeric item number from the e-mailed receipt that you get for your purchase (replacing the dashes with spaces). You can probably just put in the title of the game. I included a printed copy of two e-mails, one that shows funds being added to my wallet, and the other that shows my purchase confirmation.
So, I bought Prinny for PSP for $9.99, and also used Atlus' super sale to get Persona for $19.99. Anyway, I just got the credit for the 40 points for Prinny, and the 80 points for Persona, and also, the 999 points + 1999 points are on hold for the credits to be applied to my card.
Anyway, thought I would share. I haven't been buying a lot of PSN games since they took away the e-vouchers, but I figured I'd give this a shot. Now that I know it works, I can now get back to getting some really cool PSN titles that just were released (Pac-man, Laura Croft, etc.).