Doesn't this just pass the problem onto someone else?
Mostly no as the email are typically "sent from" from false accounts so the bounces time out and are simply lost to age. And two by having a catchall in place your server when queried to check that the email address is good will send a yes that address is good answer and allow the email to send out.
Another Short answer is that most ISP's request you phase out use of catchalls on their servers for various technical reasons.
I also have been receiving a lot of .pdf attachment spam. Not opened one yet but must admit they are quite clever as the name of the attachment and subject line are quite on target for me.
:-) ahh yes then someone you know may have been infected by a worm version and that is copying the email address book and miscellaneous email data to auto generate the spam / worms / rootkits.