User Defined Function (UDF) in master database

SQL server: MSSQL SERVER 2008 R2

I have a function which is used in more than dozen of databases. So I want this function to be accessible in all the databases by writing it only once, so I want to write the function in master database so that my function can be accessed easily.

So my question is, is there any problem in writing the user defined function in master db?

And when surfing the internet some had suggested converting function to system function. (Using “EXEC sp_ms_marksystemobject 'fn_db_name' ”).

Is there a necessity to convert the function created in master db to system function? If yes why?

Please guide me.

Thank you in advance..