http://example.com/?utm_source=June%2B2011%2BNewsletter&...
Source: June 2011 Newsletter
Medium: Email
Campaign Name: Free Summer Tickets
The moment that you store that URL in other service, a number of those tags become incorrect anyway (it is not an email anymore), and the stats you will get from it will be tainted. Campaign tags are useful, but this approach by pinboard may end up in tracking being more accurate (certainly from in terms of tracking campaign media/terms/content), at the cost of removing the campaign name.
There is also little difference between this and a URL such as http://example.com/Free-Summer-Tickets/June-2011-Newsletter?... being set up to serve the original content other than at least with the campaign tags you've got a single canonical URL using the more correct query parameter mechanism.