The disadvantages of Maslow's theory of management is twofold in my opinion:
1) Real humans aren't as compartmentalised. Maslow talks about the "needs" that humans have as if they are levels in a video game, where you achieve one and then unlock the need for another. Real humans often have needs that are complex, and intertwined with desires and dependant and circumstance, environment and many other factors.
2) Maslow's theories are too rigid. Some of the things he calls needs might not be needs at all by other people's standards. And it can be argued that his ultimate target of "self-actualisation" is also not a requirement for true human happiness.
So the disadvantage in his theories are really in the fact that, although they might make sense of paper or in theory - in practical situations they rarely seem to apply.