Are there major drawbacks/risk of using oracle blob to store files
It really comes down to cost vs. importance.  The more important the files are, the more beneficial storing them in a database becomes.  Here are some things to consider.

Pros of database file storage:


Security - The same security model your data has, same users, etc.
Backups - Usually the database is backed up more frequently, tested more frequently, and has more thorough recovery documentation.  Backups can also be faster with block change tracking.
Recovery - Old versions of files can be restored to any point in time as far back as the backups are kept.
Auditing Available.
Scalable - The more files you have the more important this becomes.  
Transactional integration with other data and code.
Flashback Query (for Oracle)
Locking Available.
Read consistency.


Cons of in database file storage:


Initial setup may take longer.
Specific expertise required.


Tom Kyte said it this way:


  If this data is valuable to your business, if this data is necessary
  for your business, if the loss of this data would damage your ability
  to do business - it has no business NOT being in the database.