Elliptical - Five days in a row or every other day?

There is nothing wrong with doing cardio everyday in and of itself, but..and this is a BIG but. if your goal is to lose fat, and not just weight than too much cardio will actually trip up your weight loss rather than help.

Far and away, it is your lean muscle tissue that is your body's fat burning furnace. The more lean muscle mass you have, the more calories and therefor fat, you burn when your NOT exercising. To much cardio, especially steady-state cardio(the kind your probably doing) will eat into your muscle tissue and actually slow down your metabolism.
The way you combat this is with proper training and nutrition.
From a training for your goals perspective you are far better doing a strength training/cardio/strength training routiune.

In other words alternate full body strength routines with cardio days in an A/B/A fashion for five to six days allowing AT LEAST 1 day of rest(or 2 days rest if you want the weekend off) As a matter of fact, for the final workout of your week I would recommend yoga if you can. It is a great way to improve flexibility, build strength and help your muscles and nervous system recover after a tough week.

As for your cardio, stay away from long, steady bouts on the elliptical. Using the machine is fine and has actually been shown to burn more calories per session than other cardio equipment. But instead, do High Intensity Interval Training, or HIIT.
This means that you do your cardio workout in intervals of high and low intensity instead of a continuous pace.

for example: hop on the elliptical, and after a 5 minute warm up do 30 seconds at 80-90% of your maximum effort, than slowdown and do 1 minute at 60-70%. Repeat the cycle for 20 minutes, followed by a cool down.
Bam! You've just done far more work in less time than your typical cardio. The added benefit of HIIT is that it helps maintain your lean muscle and it burns calories for up to 48 hours AFTER the workout is over. Of course, you can vary the intensity and duration of the cycles based on your fitness level.

Were you told not to do cardio every day as a general rule? Or so as not to aggravate your foot injury?

If it's the latter, I'd listen to whoever said that an incorporate rest days... maybe do it every other day.

If it's the former... ehhh... There seems to be quite a bit of debate on this forum how and whether people should do cardio. I do not know exactly what science is behind "steady state cardio" but I have to wonder whether it really applies to the majority of people who do 30 minutes of moderate intensity walking, jogging, elliptical.

It depends on your goals. If your looking to increase endurance or say if your a long distance runner, or training for a marathon, than consistent steady cardio is fine, but in the case of losing fat while maintaining muscle, there is no contest.

Just compare the physique of a sprinter to that of an endurance runner.

Both have very little fat and lean muscle. One has different muscle definition than the other, but I think that just comes from working the muscles differently. Both look fantastic, in my opinion.

But do those examples of extremes really apply to someone who jumps on the elliptical 30 minutes to be a little bit more active that day? For that, I'm still unconvinced.