MAD to VLC and ALC
In my humble opinion...
The example I'm thinking of in particular was Stansted - Brussels Charleroi. While Stansted is not central London and so can pick up customers from places like Cambridge and the general surrounding area, the Eurostar has a large chunk of the London-Brussels market. Ryanair was probably a bit cheaper but with 10 trains per day taking under 2h30 to a city centre it would be difficult to compete. The air route was started in June 2007 but has already been cancelled.
Easyjet used to fly Paris-Marseille - potentially a very good route with lots of business travellers, but not so great when the TGV runs in about 3h30. A route like Lille-Marseille takes about 4h45 by train so is probably long enough for Ryanair to be able to compete.
Ryanair doesn't offer easily changeable tickets and its systems don't integrate well to those used by business travel agents - making it really rather business unfriendly. The airline thus seems to be aiming at the leisure component of the market.
Because MAD is a large airport I doubt they offered Ryanair very cheap fees. Further, because it's a large airport it suffers from inevitable delays.
The only reasons I can see that MOL would choose these 2 routes are:
1) He's based too many planes / crew at VLC or ALC for local demand and needs to reposition to MAD each day.
2) As a spoiler against Spanair - neither Vueling nor Clickair fly these 2 routes. This can work if you're American Airlines putting a couple of planes between STN and NYC against Eos, but to really damage Spanair, MOL will need to deploy more planes - in the same way as Southwest is acting at Denver against Frontier.