There are a lot of ways for people who are familiar with hacking etc., to get a virus (or similar) onto your computer through applications that seem harmless.
buen sitio social, es bueno para hacer amigos y eso pero a veces te aprecen cosas extrañas como gente que no conoces te envia invitaciones, y aveces algunas personas y paginas ponen contenido de adultos
As others have said, there are loads of privacy issues with this site. Also most of the adverts are attempts to scam or phish details from you. A lot of content on the site is inappropriate for youngsters as well.
Anyone can post whatever they want - they can post inappropriate pictures and sexually explicit blogs or items, and chances are that even though they'll be spotted and removed in the end, these profiles can hang around for a long time before being detected. Not good for children at all.