I was having a discussion with a developer at work on the issue of should a table use default values. Is there a hard and fast rule on this or is it a gray area in best practices?
My rule: if many records will use that default (at least initially) then I like to use it as a default. For example, an image table for products in an online store might have a default path of images/NoPictureYet.png. Eventually, those will get replaced, but for batch loads of data where the pictures simply don't exist yet (and maybe most of them never will!), a default makes sense (to me, at least).
If there is no sensible default (such as "first name" in a customer database - I don't want MY name defaulted to "FirstName"), then I make it non-nullable and no default - it's the application's responsibility to ensure that a correct value gets entered.
But no hard and fast rules on this. It all varies a little ;)