What are the disadvantages of jQuery?

1: Sometimes hard to predict performance of selectors

2: Some methods don't chain (those that return values) but there's no marker within the API

3: Some methods have different call semantics (like val() on different form field types, or any of the methods that only operate on the first element of a set)

4: Sometimes can be difficult to evaluate plugins because of all three of the above.

for more check this
http://stackoverflow.com/questions/5347629/drawbacks-of-using-jquery