Well,the difference is ride-sharing is more or less tolerated,if it's not for profit. Very few people offering shared rides make money out of it.It's usually paid,because it's more about sharing expenditure.

UberPop,on the other hand,is a private taxi service.It's not about someone saying he goes to Nantes and has room for 4 people,for a 15€ fee.

Given the price of the train,the development of ride sharing and inter region bus travelling(which was still illegal a few years ago),is a good thing.

I cant believe how insanely expensive the train is today.The SNCF also stopped providing a lot of services (low cost train,stations,...)they deemed not profitable enough just to push for the high speed rail.in 2005,you could do Paris-Nantes for 15€. It took 4 hours,but who cares.

Today,it's 50 up to 100€ + if you dare book a trip on the same day you're travelling.