Having a unique email address for each shared label allows you to get even more organized. You can use this email address to do things like sign up for online newsletters or give it out to external business partners, so that these emails go straight into that specific shared label. Hello uncluttered email inbox!
Example If you want to collect feedback of your customers, but donot want to create a separate google apps account for this. You can create a shared labels called 'Feedback' which will then have the email ID feedback@<<your_domain>>.com and all the email sent to this will be collected in the label 'Feedback'. Similarly you can create labels for 'customer support'...The use cases can be many.