Some Points on Cookies Drawback.
1) Even writing Cookie is a great way to maintain user interaction, if user has set browser options to warn before writing any cookie or disabled the cookies completely then site containing cookie will be completely disabled and can not perform any operation resulting in loss of site traffic.
2) Too many Cookies: If you are writing too many cookies on every page navigation and if user has turned on option to warn before writing cookie, this could turn away user from your site.
3) Security issues: Some times users personal information is stored in cookies and if someone hack the cookie then hacker can get access to your personal information. Even corrupted cookies can be read by different domains and lead to security issues.
4) Sensitive information: Some sites may write and store your sensitive information in cookies, which should not be allowed due to privacy concerns.
Test Cases for Cookie Testing >>