No, definitely not XD. I would drop dead before I would lend my PSN account to stranger so they can get a DLC for free. If anyone did ever try this on me I would send a very "educated" message, borderline to violate Sony ToS.
I could care less if you don't have money to buy a DLC or you credit card is blocked, whatever. It's my account, with personal info. They could even steal it from you (if for example your email password is the same as psn).
As far downloading content on another ps3, that's fine, Sony actually intended to be like this: You can download any content from a psn account to 2 ps3 at the same time. It doesn't need to be your home console for this to work.
Edit: I believe you can report those messages to Sony as fraud or attempted account stealing.
"O Admonishing melody, arise in the of Necromancer. Mystic Cage"
PSN ID: Otonio_Bruno