The biggest disadvantages of bitcoin is that bitcoin can be stolen by anyone in many ways. Bitcoin service providers can be hard to trust, but even if it is, we must to trust bitcoin. You joined in the field of bitcoin then it means you trust it. There is a lack of acceptance, lack of protection because it is not considered as legal in most countries in the world.
I think the biggest disadvantage you'll encounter in Bitcoin is scam. You give your trust fully that's why you invested Bitcoin to a certain person but that person just made fool of you and get all your BTC. You have been scam and that would be a big loss.