Well.. the majority of Poskim shun at the idea of a wig, there are scary stories of the Chatam Sofer, the Stipler, Baba Sali and Hacham Ovadia Yosef.
There are those who are Makil.
Hacham Ovadia in Yabia Omer vol.V, E.H 5: offers three reasons
- They very much resemble a woman's hair
- They are eye catching, in actually being nicer and more lustrous than real hair
- Early authorities held them to be forbidden, going according to the Jerusalem Talmud, Ketubot chap.7, halacha 6.
Rav Ovadia Yosef also refused to give Brachot many times to woman who wears a wig, and many such stories profess to this, when then changing to a Kerchief he would bless them, and what they wanted usually materialized.
However, there are those who are Makil, but with strict guidelines, such as that it shouldn't go past the shoulder and it must not be fancy. The most famous Poskim are Reb Moshe Fienstien and the Lubavitcher Rebbe
To summarise, it is best to distance oneself from Wigs, as they bring in many problems.