I have been running an online marketing agency for the last 5 years and dealt with many so called seo consultants. Unfortunately there are many individuals who promote themselves as seo consultants but have very little technical understanding of search algorithms.
In many cases business owners will have limited knowledge of search engine marketing and consequently may be unable to determine the ability or quality of work carried out by an external seo. There is an element of trust in the early stages and only after a period of time do businesses become aware that they may have been misguided. Consequently clients can become disillusioned with seo or sme's after spending considerable money and seeing minimal returns.
My advice to any business owner who is considering outsourcing seo is too initially gain some understanding of the process. To see real results from search marketing businesses must be prepared to invest long term but understandably may be hesitant to sign long term contracts.
One possible solution is to hire established seo professionals to monitor outsourced work and ensure quality guidelines are being met. We offer this service and in many instances companies find working with us provides them with the confidence that there investment in seo proves beneficial.