I'm French and this is honestly the very first time I ever heard of this service. I'm not in the target audience, but 8 million users in France? Riiiiiight, that's more than 13% of our total population, roughly 20% of all French internet users, or one Facebook user in three. It's roughly equal to sum of the population of the top 3 to 10 most populated cities in the country along with their whole urban surroundings, or 2/3rd of the population of Paris.
This figure makes no sense to me. Even assuming it's targetting a very specific population that I share no connection to, it's still a ridiculous figure. The biggest (in revenue) dating website in France (and apparently, in Europe, too) is Meetic. It had less than a million registered users in december 2010 in total, including other companies in the group.
After a quick search on independent consumer satisfaction services, turns out there are a lot of people whose accounts were created through fishing or the likes, or even without consent. Just by reading the tons of user comments, this really looks like a major scammy, fishy, spammy and illegal service (illegal at least in France, since it refuses to comply to our Privacy & Freedom directives).
There are some satisfied comments, too, so this service probably works well enough in some ways, I just can't take these figures at face value.
I personally know multiple, sad people who maintain 10+ fake facebook acoounts in order to create fake images of themselves. I can easily imagine really high rates of those people in such a network. Especially if there is nobody trying to avoid this kind of accounts.
I don't know if there is any benefit you could get by having many accounts, but if there is, I'm really sure it is used a lot.
I know a lot of people that have multiple Facebook accounts, some are kids that want to push different updates to different people for example, or a "games" account.
Others are men with a "dating" account and a "family" account.
I guess the same happens in Badoo. Also, they must have a lot of dead accounts and count them (much like Microsoft does).
Their numbers do seem inflated, I don't know how much (50%? 100%?). I'm their active users must be at least an order of magnitude lower (my own account is inactive at the moment).