When you consider that facebook has taken steps to force more ads on their users despite knowing that users don't want them and will actively go out of their way to reduce them, I wouldn't trust them.
Facebook also changes users settings very often. Just one small example, I have to reset my feed back to newest first on average 3 times a day, and that's not the only setting they screw with, though the others are either less frequently, or I don't notice it as often. Because of that, I wouldn't trust them.
Their platform isn't as stable or concise as it might appear to a single use as they 'test' different components on different uses, and don't tell anyone what version of which component they have. This would be horrible in a store platform, so I wouldn't trust them.
Facebook has done social/psych experiments on the users without their knowledge or permission. Though it may have been useful to some segments of science, it still was inappropriate and is a further violation of trust, so obviously, I wouldn't trust them.
The long and the short of it is that Facebook can't be trusted.
A store platform by a company that has ethics as low as Facebook should be trusted even less as that deals with your money.
This is likely to be a disaster in the making.