Well, today I've heard of "sequenced field" for the first time. Google found some references, and it made me think that this is a) Oracle Applications term, b) doesn't have anything to do with Oracle. I'm unable to help in any of these areas
Using sequence for populating column is good thing as you can always maintain referential integrity through other fields of column. Few things for using sequence usage are:
1. You should make sure that various sequences for various tables should not contradict each other. (Specially when you join/compare).
2. Application logic should be intelligent enough not to use same value (should not select/use curr.val or next.Val)of sequence in different sessions at given point of time.
3. Sequence always populate NUMBER type field. Its length should be long enough to serve your application/logic for desired time.
I would say first point will be least important as logic shall never reached at any point when comparison of sequenced fields make any error/bug generation in application.
Other then these I heard their may be issues in sequence during Export/Import. But havn't got any information for this.