Hi, i am building a site at the moment and i am trying to decide whether to add Captcha to my site to protect the following:

- create account form
- contact form (as it is saved in the database)
- change email form
- change password form

01 - do you think this will p*ss users off - i don't think it will as they really will only ever need do enter the Captcha once...

02 - i am surprised to see that Facebook and Twitter do not use them, how do they stop robots from processing multiple forms

03 - what is your general view / feeling on using Captcha's