Putting too much oil in a car

If you took your car for a service, and the shop put about 1.1  liters of oil too much in your car. What can go wrong and is the most common problems that occur usually when this happens?
Please no dumb and dumber jokes ;D Its not me who made this mistake.

I serviced my Kuga 2.5T myself for 3 years in a row. But as I am thinking of trading it in about 2 to 3 years from now, I wanted some service stamps in my cars book. So I took it to a garage. When I got it back I did not check anything as it was at the ''professionals''.
My car uses very little oil, I did not really had to top up the oil between services so I did not notice the extra lot of oil in my car as I did not think its necessary to check the level. Now, about 6 months after the service my car started leaking oil. Before the service, not a drop. It really was up to now just as reliable as a new Toyota Corolla.
It seems like the camshaft seal is the culprit. Can too much oil cause this to happen due to extra pressures generated by over a liter of extra oil?

I want to be clear, I do not intend to sue for damages, but would like to know why my car started to give this problem. Is it because of the overfilling of oil, or is it because its not a Toyota ;D