Cryptocurrency is now an established medium of trade and has been profitable for most of the members of the community. I know that most people have heard of BTC in different avenues of communication may it be in SNS, blogs or even news the only thing that's keeping them from really utilizing crypto is their fear of it. Still, Crypto has been advertised and made known to the public. We all know that advertisement is a necessary method to invite investors.What could be its negative effect to crypto?
What do you mean by "advertisement" here? No one is advertising crypto, and still less the channels you mentioned. Well, in fact, developers of a number of coins do advertise their coins, through airdrops or elsewise, but that's not what you seem to mean here. Anyway, if you refer to publicity, then any publicity is good, as the saying goes. Obviously, good publicity is better than bad publicity, but here lies the main problem. It is often difficult to say or distinguish between what is good publicity and what is bad one.
To sum it up, it is almost impossible to say in advance what net effect some news will have, especially long term. It can even be the case when some form of press or news coverage may cause visible, undeniable damage to the image of crypto (like its use in the DarkNet) in the short term but over the long run it may actually turn beneficial as people are prone to forget bad things about something but their awareness of it will nevertheless persist.