Today most, if not all, websites worldwide use cookies. However, cookies are rather limited, as they can only store up to 4KB of data. Moreover, many developers claim that because cookies are sent to the server with each HTTP request, large ones can consume considerable network bandwidth, hurting performance. Another important criticism against cookies has been written by Remy Sharp in the co-authored book Introducing HTML5. This can be potentially catastrophic for mobile connections. Another important point to keep in mind is that if you have European visitors, then your site must comply with the EU E-Privacy Directive from May 26, 2012. If you never heard about this, take a look at Why Your Site is Now Illegal in Europe.