I am having several sign-ups per day now from non-real people...! I use double opt-in, so none are added to my list, but these email addresses are usually from non-existent domains. They just sit in my unconfirmed list.
What I would like to do is two things:
1. Find out where these are all coming from and therefore how I can stop it from happening in the future
2. Delete the unconfirmed from my list - I can't see a way of doing that
The only place I have sign up forms is on my website and the forms are all Campaign Monitor derived.
It seems like all of those fake addresses are coming through your subscribe form since they all have '(joined via API)' mentioned in the subscriber details page. It looks like bots are adding addresses through your subscribe form and then your site is adding them to the list using the API. Thankfully they are stuck in the 'unconfirmed' tab, but to keep more from being added I'd recommend using captcha on your form so only humans can subscribe. There's several captcha services out there, even Google has a free captcha service so hopefully you can find what works best for your site.
There isn't a way for you to get those fake addresses off your list, but if you email support we can remove those for you if you wish.