I'd like to have an independent opinion / samples of whether **radiobutton group should have an option selected by default**: some colleagues tend to submit missing choice as an issue, while others say this is OK. However, I think there are several samples where NO default choice seems to be fine:

```
Please select your age:
( ) 16-20
( ) 21-25
( ) 26-30
( ) 31-40
( ) 41-50
( ) 50+

```

From where I sit it looks like for that case NO default selection is fine, otherwise some users may left that option unchanged, while it may be especially important according to business logic.

One more option is **sorting**: ASC / DESC choice, while at the same time no sorting is still acceptable by application / business logic.

To be more specific and not to make this a discussion, please provide specific samples where default choice is obligatory, and where it is NOT.