Error: Custom field limit has been reached for this data type

Error: Custom field limit has been reached for this data type

The ability to add custom data fields for items is a good addition but when I tried to add a third "decimal" type field the following error was received:

Almost there, but...
    • Custom field limit has been reached for this data type.


Is there in fact a limit to the number of custom fields you can create for each data type?  If so, why?