EF: prescriptive classes and IPOCO "only", what a great idea!
Some of you saw a petition against EF v1 which is a nonsense in my opinion.
I read an interesting question on the msdn forum and I think my answer illustrates why it's great to have a common base between all entities.
So of course, with POCO you can do this by using reflection and by reading the metadata but it isn't great!
Of course you can also implement yourself some common interfaces with POCO but you can forget it on one of your entity type. With IPOCO (and of course with prescriptive classes), you are sure that every entity type implements IEntityWithKey.