A simpler, more contrived example, would be to create a new function create_and_send_email! and place the creation logic and email sending logic in there. And now, when the developer uses the service object, she has the ability to choose between just creating the contact, or creating it and sending an email.
@contact = contact
def initialize contact_jack, email_jack
@contact_jack = contact_jack
@email_jack = email_jack
def do input
# validate input
contact = Contact.new
email = ContactEmail.new
action = CreateContact.new
result = action.do ContactJack.new, EmailJack.new
Obvious is on github, you can read more at http://obvious.retromocha.com
create_contact!(:send_email => false)
Plus he should probably just break the send_email method into it's own method, which he can then call depending on if create_contact returns successfully.