Custom fields with limited length not validated

Steps to reproduce:

1. Create a Custom field of Type text with a length set to some small number.
2. Access a form containing that field (profile or built-in forms)
3. Enter some text in the field that exceeds the specified length & submit the form.

Expected results:
Form widget should not accept characters beyond the specified length. If a string that is too long is submitted, form should not validate, and user should be notified that submitted value exceeds the allowed length. If a value is submitted via API that exceeds the limit defined for the field, the API should return an error.

Actual results:

Submitted value is silently truncated; there is not alert to the user that data has been lost.