For reasons I won't go into, one site I work with has made the move of blocking certain countries from the Middle East and Far East by presenting visitors from those jurisdictions with a simple message.
Around the same time, a lot of longtail rankings dropped from Google.com which could be due to any number of factors but I need to try and rule out if this is one of them.
Msg#: 4472554 posted 10:25 am on Jul 6, 2012 (gmt 0)
@phranque: geoIP package used in PHP code
@grippo: Google from those local jurisdictions will be yes but (in theory) only from those areas. Also, looking at the results in google.com, it seems to have snippets from the page I would hope Google is seeing rather than from the simple "go away" message, so that's good at least.