There are many mining pools who take fees from you for you desired Bitcoin addresses as they have more computing power dedicated to the network instead of individuals computing power
Those addresses are also risky to use, even if the mining pools are legit.
As they already have the private key they shared with you, your address is already considered exposed since day1.
And a hacker may intercept their message, or even hack their database.
So, the best would be to avoid those services at all costs.
It is that simple, all that surrounds vanity addresses seems like a waste of time, if you want one then you need to find one by yourself, if you use another service then your keys are exposed from the beginning and the proverb of not your keys not your coins applies here, now on the other hand do people actually believe that those rich people are going to take the time to generate a vanity address themselves and then ask for donations? If true they really need to learn how to spot scams as it is amazing the dumb scams in which they fall.