For FileMaker its not so much as issue, but in most SQL naming conventions, spaces are not used as well as some other things. If ever you want to use FM as a data source it it just easier for other systems ( and their developers ) to use standard conventions.
There are some developers that come from more traditional development background as well as those that deal outside of FileMaker a lot. Then there are also a lot of developers that dealy almost exclusively with FileMaker.
So really it becomes a personal preference.