Wirelessly posted (8820)
First, don't use your @carrier.blackberry.net anywhere it can be harvested. Don't use it for registrations. There is no spam filter on that account.
Second, enable spam filters on you other email accounts.
Do not click on any links in spam emails. On the blackberry, do not get images in spam emails. And do not click the unsubscribe link.
Finally, the risk of the BB being infected is very, very small, probably zero, unless you give permission for it to install.. But you can pass along malware in emails when/if you forward to someone else.