Are social exchange websites safe?

[Thanos Greece]

There are some websites where you can get free Facebook likes, Tweeter follows or YouTube subscibers and alot more...

I have been using one of these sites of my old YouTube account, and I can say that I got about 200 subscribers. I will not post any links here because I don't want to advertise, however I am still wondering if it's "safe" to use them.

I was thinking though that there is no legit and illegit ways on promoting your contect while if you try to help your work to be promoted it's legit, in any way.

In other words, it might be "unfair" I don't know how to express it, I need your opinion on that, if it's safe and legit or waste of time.