What expectations the unreasonable a SEO?
Typically it would be something like "We would like to rank page 1 for high commercial terms inside 90 days using safe SEO".
Of course we tell them that isn't likely - or in many cases possible. We emphasise the long tail (where the value normally is anyway), the need for traffic diversity and pledge to do our best with their target keywords.
However, no matter how precise and detailed you are in pointing out the value of the long tail and traffic diversity. 3-6 months down the line the client is likely to be questioning movement for the "location/vocation" keywords. Of course there is normally positive movement. Typically they will have gone from not ranking at all to page 3 or 4 or similar.
Traffic levels will be up, revenue will be up. ROI will be good - but the client still wants a long chat about ranking for "Lawyer in London" and "Why is that crappy business down the road ranking number 5 on page one and not us".
Typically the worst clients are those that do not enter into any level of partnership with us. They aren't interested in providing content/value, and just want to pay the money and see the results. Fair enough of course, that is their prerogative. They are professionals in a different field with no interest in IM.
It's so much easier when you and the client agree base level performance indicators early - and those performance indicators are based on things that REALLY MATTER like ROI, profit and sales.
The emotional tug of wanting to be seen on page 1, and higher than their competition (who they often know personally and have done for many years, and see regularly at meetings and when tendering for work in there own profession) remains high.
It's emotional then, rather than practical more often than not.