How to Deal With Email Only Contact Records
I'm not sure you'll find the email only contacts will really be noticed with day to day operations.  We have some, granted less then 5%, and I rarely come across them.

Think about the kind of queries your users do with contacts, like using the quick search box in the upper left hand corner and what situations they would likely pull up a bunch of email only contacts.  You have to be searching for a name or email that matches an email only contact's email.  (When it does, I often find a matching contact.  The contact is fully in civi but they gave a different email address when getting on an email list.)

I don't think there is a way to by default exclude them.  However, there are a number of ways you can make it easier to isolate them in queries.


You can create a smart group of everyone else.  (query builder, individual, last name not null).  Then use that group for queries.
You could usurp one of the privacy options if you aren't using it, like "Do not Phone" or "Do not trade" or "Do Not SMS" and exclude that option in advance query.
You could create a new contact type for the email only; though, since it will be a child of individual, there might not be too useful.