What are drawbacks of ideal clamper?

[lazyaditya]

What are the drawbacks of ideal clamper ?

Some body told me that in case of ideal clamper , capacitor does changes its voltage even if i/p voltage is decreased.
What i think is isn't it good that clamper is ideal.

 

[NascentOxygen]

Can you include a link to an example of the circuit you are talking about?