It's easy for me: I haven't registered with either of these services, so I easily delete all emails referring to "my" accounts.
I suspect my question answers itself, finally. Those who are web-savvy trust that their services are also web-savvy enough to know not to send out such emails, and those who aren't don't realize that they're being taken--and also don't find their way to blogs such as these.
You may wonder why I'm bothering to notice such spam, which is, I recognize, fairly anodyne. The fact is that I've closely guarded my private email addresses. The only spamish emails I've ever been inundated with have been "calls for papers," a list-serv that basically destroyed my favorite email address and my professional confidence. Never signing up for more general mailing lists, never providing a true email on webforums, never making myself available in that way sufficiently protected me and my accounts.
So now I have an account, about four months old, that is available to spammers via blogger and my blog-handle. It gets thirty-odd emails per week, neatly divided between paypal and ebay references.
I offer this as data for someone. Warnings for others.