Friendship can never have any disadvantages.
Misunderstading the id,gender and age etc; may be disadvantages.

I am yet to feel it. The characters of human are the same, be it real world or the net world. But I think that the net world gives an opportunity to gloss over one's deficiencies that may be clearly visible in real life interaction. In that sense the net friends (or acquaintances) may give some false impression and one may be quite disappointed to see the real character which is quite contrary to his expectations. But in real life also, we may sometimes interact with people who pretend a lot and the real character comes into open much later. So in a way the same facets of human character are seen everywhere and every way. The differences are in manifestation and forms.

Bas yahi ki ham sabse ru-b-ru nahi ho sakte........

That "friend" can disappear any time. After investing so much in that so called friendship you are left empty handed.

Somebody can deceive ,cheat you so beware

One day u r going to be cheated that is for sure

I dont see any disadvantages. Everything depends hw we interact.