Are you planning on storing blobs in Innodb tables? If yes, think again. According to the manual,
InnoDB stores the first 768 bytes of a VARBINARY, VARCHAR, BLOB, or TEXT column in the row, and the rest into separate pages.
This translates into slower retrieval for blobs. However, InnoDB can skip reading blobs if they are not in select column list.
One solution for this is to keep blobs in a separate myisam table and do a join when you need the blob column.