Lo correcto es: Buscar A alguien y buscar algo Buscar alguien es incorrecto En el caso de Facebook, cuando dice "busca personas" o "busca gente", se refiere a algo muy general e impersonal, igual que si dijera "busca profesores", "busca enfermeras", etc., no se refiere a alguien en concreto.

As you probably know, in spanish you can change the order of the words and the meaning will remain the same. In the sentence: Juan drinks water the possible ways to say it is: Juan toma agua Agua juan toma Juan agua toma. There is no confusion since 'agua' is an object and there is no posibility that the water driks Juan. But when the object (or second noun) is not an object and the verb can induce the posibility of a confusion or missunderstanding the preposition 'a' is needed. In the sentence: Juan looks for Pablo. Juan busca Pablo Juan Pablo busca Pablo Juan busca. It is impossible to determine who is carrying out the action, for that reason 'a' is needed because 'buscar' is a "verbo transitivo". So,in all the sentences: Juan busca a Pablo a Pablo Juan busca a Pablo busca Juan All of them point out that Juan is looking for Pablo and not the other way around. Adding an 'a' will aid you to rearrange the whole sentence with out inducing confusion. A way of know if a verb is "transitivo" is by looking at its definition in a dictionary. Ther will be a small tr. . But as a trick: if you feel that there is a chance of confusion, this is, if the "object" can carry out the action aswell, add the preposition 'a'. As a final comment, "busca personas" refers to an order "Busca personas!" but obviously without the exclamation mark. :P

"Busca personas" is an imperative sentence. It could be an order or a suggestion. "Busca a personas" is a statement. It is just an advice. Does this help?

creo que no hay diferencia real en el significado, la preposición a junto con la "de" tienen muy variados usos. En este caso sirve para introducir el complemento directo, en mi cabeza suena mejor con a. Tengo entendido que no se debe poner solo si lleva a redundancia o confusión como por ejemplo en: "busqué a un carpintero a mi madre" la primera a no me suena bien pues también esta usada para introducir el complemento indirecto