If a NEW donor makes a donation and only supplies their email address*, the displayed name is blank in WordPress civi 4.6.4 and above. (*This can happen when someone donates directly through PayPal, civi only retains the email, or sometimes in a "pay later" situation when only an email is required.)
The email address does not show in the contribution dashboard, contribution searches or the soft credit section on the donation tab for a contact.
If a donor already exists with just a email, then it's peachy and shows the email name. But if you make a new donation with a new email address there's no displayed name. (see attached) As a workaround, you can go into the contact, press 'add or edit email' and then immediately press save and civi will then start displaying the email properly.