Column of generic/variable type?
Why BLOB ? 
Why not string or varbinary(max) or nvarchar
Dot Net Nuke in their database inside table UserProfile have generc column 

CREATE TABLE [dbo].[UserProfile](
    [ProfileID] [int] IDENTITY(1,1) NOT NULL,
    [UserID] [int] NOT NULL,
    [PropertyDefinitionID] [int] NOT NULL,
    [PropertyValue] [nvarchar](3750) NULL,
    [PropertyText] [nvarchar](max) NULL,
    [Visibility] [int] NOT NULL,
    [LastUpdatedDate] [datetime] NOT NULL,
    [ExtendedVisibility] [varchar](400) NULL ....