Advantage:

1) Maintains the state for autopostback event.
2) Easy to use.
3) No ServerSide resources required.
4) Passed into HiddenFied.
5) Basic enncryption algorithm is applied when passing the data.

Disadv:

1) When large data is there then perfomance is issue.
2) Good Hacker can get the data very easily.

Advantages:
- No server resources required
- simple implementation
- automatic retention of page and control state
- Enhanced security features. The values in view state are 
hashed, compressed, and encoded for Unicode implementations.

Disadvantages - Because the view state for a given page 
must be kept on the server, it is possible for the current 
state to be out of synchronization with the current page of 
the browser, if the user uses the Back feature on the 
browser to go back in the history.For example, suppose the 
user goes to Page 1, then clicks a button to go to Page 2, 
then presses Back to return to Page 1. The current page on 
the browser is now Page 1, but the current state on the 
server is that of Page 2. Advantages - On ordinary Web 
Forms pages, their view state is sent by the server as a 
hidden variable in a form, as part of every response to the 
client, and is returned to the server by the client as part 
of a postback. However, to reduce bandwidth demand when 
using mobile controls, ASP.NET does not send a page's view 
state to the client. Instead, the view state is saved as 
part of a user's session on the server. Where there is a 
view state, a hidden field that identifies this page's view 
state is sent by the server as part of every response to 
the client, and is returned to the server by the client as 
part of the next request.