Thom,
There is a thread on this by Adam Waterson.
EU ISSUES
https://community.marketo.com/MarketoIdeaDetail?id=08750000000I4ZfAAK
http://community.marketo.com/MarketoArticle?id=kA050000000KzYg
http://community.marketo.com/MarketoDiscussionDetail?id=90650000000PBuAAAW
http://community.marketo.com/MarketoDiscussionDetail?id=90650000000PEjfAAG
The article "Marketing Automation and the European Privacy Laws" would be a good start
https://community.marketo.com/MarketoArticle?id=kA050000000L6ELCA0
You can find extremely detailed documentation in 24 European languages, including the legal nuances for specific jurisdictions such as Germany and Holland, the most strict ones. Some Dutch companies go as far as traditional post inviting users to visit their website and register.
http://europa.eu/