>>You also can create multiple trees (you'll need different "accounts" to do that, <<
You only need ONE user account. You don't "create" a tree on rootsweb.com world connect; you upload a GEDcom and can upload as many as you want.
One user name account is good to access 3 Ancestry.com owned sites.
1) - Ancestry.com (Ancestry.com is the name of the parent company AND the US website). You can also use your user name and password to sign-on to Ancestry.uk, Ancestry.ca, ancestry.de, etc.
2) - rootsweb.com
3) - mundia.com
These 3 sites all have some free elements.