[W.Smith]

Originally Posted by kevgermany

They get in the way and increase bulk.

Not if you use the proper 'travel mode' and put the hood on backwards when not shooting.

They affect your use of filters.

No: UV or CP filters (never stack filters) are not impeded by a hood. Cokin-type filters and filter holders and hoods don't work together well, but with digital you don't need those physical filters, because you can add 98% of those filter effects in post production (and that also saves you a lot of time, hassle and fidgeting with them on location!).

When reversed they often cover lens controls.

So what? You don't need lens controls when you're not shooting. And since you should always use the hood when you are shooting, it cannot be reversed at that time, so it cannot be covering lens controls.

Take up too much space in the camera bag.

Not when reversed in 'travel mode'.

Can slow you down if you fit to lens reversed to save space.

So anticipate! Think ahead: if you might want to shoot at an instant's notice you need to switch on your cam in anticipation anyway. That is also the moment you should fix the hood (correctly).

Many times you don't need them, so given the cons, why not leave it off, unless you need it. Even then you can often shield the lens with a spare hand.

Hoods are useful on a lens. They are useless in the bag.
Shielding with a spare hand means compromising camera stability!

Doug's comment on the pop-up flash is valid of course. But how sensible is it for people with 2,000 bucks worth of camera in their hands (or more) to use that peanut flash?
For 'serious' photography I use a 'serious' flash gun.

Doug's comment on macro and hoods is entirely valid of course. But then, macro is a very special situation, where there usually is plenty of time to set up. Enough to add-on or take-off the hood as the situation warrants.

So for me the rule-of-thumb is:

Never shoot without a hood!
(unless there are very special circumstances)