This question gets asked a lot and indeed if you should use Hashtags at all? In answer to that 'yes' If you do it correctly.
The biggest mistake is sometimes I see Facebook posts which multiple Hashtags, which is a big NO NO and dilutes the impact and presence of the original post. Try and remember that LESS is MORE. The ideal amount of Hashtags should really be NO MORE THAN TWO.
A study by 'Social Bakers' showed that:
You get the picture!
You have to remember that Facebook handles Hashtags a little different to Twitter insofar that it treats Hashtags as a type of category or relevant sections AND a way to start a relevant conversation. If you're a business you should ideally break your services or products down in a category or sub-section of your business. And keep it local i.e. #WebDesignSouthport or #SocialMediaServiceSouthport.
Remember to keep the keywords relevant to your business or conversation and NO spaces between Hashtags