Even if you are theorically not limited in the number of fields, keep in mind that SQL has its own limitation about the number of characters that a view can display for one record
As long as the system is base on views like
inner join YOURENTITYCATEGORY on ...
You could be confronted to this SQL limitation. (that happened to me with SQL Server 2008, so I had to adjust and limit the fields I did select in my views and to watch carrefully the * statements to fix the case)
Note that the size of each fields is probably more important that the number of fields.
Alexis is right about the fact that defining if a freaking huge category is really what you really need is the first thing to do.