Staying safe online has become a very crucial issue. You need to ensure that your account is safe not only for your sake but also for the sake of the people that follow you on that site and also those that are your friends e.g. on Facebook. Free followers can be a very lucrative offer that you may want to take up. You may need to ensure that the whole process is safe. Most such providers use spam and thus end up spamming your account which may result in spam for your followers.
This is very dangerous as your privacy may be compromised. Other than that, the privacy of your followers may also be compromised. Eventually your online integrity may be lost once people figure out that you were using free followers to gain popularity or to promote your business. To avoid this you could try doing a little research on the site providing the service before signing up. Read the comments left on their comment section by their previous customers. Pay particular attention to those raising complaints and what their issues were.