The correct answer to this open question is the following.
Online marketing research seems to be the wave of the future. The drawbacks I see associated with conducting surveys online are those survey companies do not respect the privacy of the data and information shared by people. They said that they "protect your data and privacy" but later you find that other companies send you adds and marketing campaigns and yo have never shared your data with those companies.
Yes. privacy issues are greater with online surveys than with other forms of administering surveys, such as phone, face-to-face, or mail because that information is easier to handle and share online with what they called "partner companies."
So next time you find an online survey you have to think twice and wonder what is going to happen with your data.