Well, it supposedly has a lot of potential as a propaganda platform, and with an election coming up, at least some are worried about that. A writeup on Stratechery: https://stratechery.com/2020/the-tiktok-war/
You mean the same way his campaign uses facebook and twitter as a propaganda platform. Thats really the most important issue here. He can run political ads on both platforms and they do nothing about it. Tiktok reaches a gen z and millenials and he can't do anything about it.
On those platforms, ads are called out as ads. This would be more like viral marketing on those platforms, except that it doesn't have to pass your friends' sniff tests in this case, so it's much easier to push whatever you want into peoples' faces.