[batou]

The problem is that it's a complex trade off whichever way you turn. Knowing which trade off to make is difficult for many people as it requires knowing all of the assumptions and conditions that are before and after the call as well as how the expression will react under all conditions. Add complex predicates to that,which the language encourages and it's pain.

[wvenable]

Except your example isn't a complex trade off -- it's just how it works. FirstOrDefault() returns the first or a default. It's right in the name? Which is first? Well you better provide an order if you care. If you don't care, don't provide an order. There is nothing complex about that at all.

It almost seems like your looking to blame Linq for what is clearly poor database and project design. If you have poor design you're going to have problems no matter what.