security DNS security hosting on NC

i have a dozen domains which i cant add to my NC hosting account it says already hosted with another account.

Hard to say anything without seeing the domain in question (your domain).

In any case, I see two possibilities:

1) *what you wrote*. Somebody somehow adds tons of domains to their hosting account which is set to forward everything to the lander in question (amazon hosted). It may well be that they track zone changes. Maybe somewhat similar to what some folks do with newly regged expired and dropped domains. They do not win an auction at namejet/snapnames/dropcatch, or maybe do not participate, but still frequently add freshly dropped domains to their sedo/bodis/parkingcrew/etc account. Legitimate auction winner changes dns to the parking company but is unable to add the domain to his parking account. A few days - and the confilct is fixed. In the meantime, somebody else received potential parking income.

2) NameCheap may be doing the same for domains that do point to their hosting, but are not yet added (or not correctly added) to any customers account. They do not even need to know the exact domain. Traffic for some domain received, but the domain is actually not in the system? Let it go to 1 click ppc page instead...

Added: Some hosts are routinely doing it for 404 traffic if the customer did not bother to configure .htacess or smth. similar serving 404. Yourdomain.com? They show your website. Www.yourdomain.com? Also, your website is shown. Www.yourdomain.com /abyrvalg.html ? No such page is hosted. Parking ads are shown instead, since it is what the hosting company elected to show,