In the interests of science I have just driven with the blinds closed for around 20 miles over West Yorshire's finest A roads and around 200yds up and down the cobbles of Station Rd in Guiseley.

Blinds stayed closed - even over the cobbles.  Those clips do look very flimsy though.  Can't see how they would stand up to a lot of opening and closing.

Mine will stay open!!

My Roomster, May 2011, had this problem on bumpy roads, It also liked to open the blinds in hot weather, and also frosty weather when parked. Warranty fix had 2 magnets fitted which although unobtrusive, would probably hold the car to a steel roof beam they are that strong. I never open the blinds and consider it a complete waste of time, so a self opening one drove me crackers.