E-mail addresses are used for lost login information only.
You can delete your E-mail address by changing it to email@example.com from your recipes page (You do not have to Verify it, It will overwrite your E-mail address when you change it - You must be logged in).
You can remove your username by changing it to somthing else from your recipes page (You must be logged in).
Cookie named "PHPSESSID" To remember most of your preferences, your time zone for recipe dates and to show if you are logged in or not. (gets deleted when you close your browser - Session cookie)
Cookie named "E-Liquid_Recipes" If you Register and each time you login to make your login more secure.
Cookie named "UserName" If you Register and each time you login so you don't have to type your username in the next time you log in.
Cookie named "TextSize" If you change the text size to remember your preference.
Cookie named "mobile" If you use the calculators to remember if you are using a mobile device or not, So you get the correct calculator for your device.
(More Information about Cookies - wikipedia)