Are there good reasons not to use an ORM? [closed]

Answer 1

I worked on one project where not using an ORM was very successfully. It was a project that

1. Had to be horizontally scalealbe from the start
2. Had to be developed quickly
3. Had a relatively simple domain model

The time that it would have taken to get NHibernate to work in a horizontally partitioned structure would have been much longer than the time that it took to develop a super simple datamapper that was aware of our partitioning scheme...

So, in 90% of projects that I have worked on an ORM has been an invaluable help. But there are some very specific circumstances where I can see not using an ORM as being best.