[fauria]

"If the application really is schema-less and has a lot of optional parameters that do not appear in every record, serializing the data in one column can be a better idea than having many extra columns that are NULL."

Why not just use a document oriented database instead? Seems like a good use case for MongoDB for example: https://www.mongodb.com/compare/mongodb-mysql

[wesd]

Also the assumption is that you don't need to report on the data. If you need to report on the data then you might need to create index on those columns for performance which you can't do on a blob.