I have just discovered an issue if you store serialized objects into MySql.
At first I used fieldtype TEXT. If in this case somebody edited another field of such a record with phpMyAdmin and pushed the save button, the stored object in that record got currupted and the object could not be deserialized and instanciated anymore.
We now use the fieldtype BLOB instead, so phpMyAdmin does not give you the chance to edit the fieldcontent. And it works.