It seems it would depend on your learning curve, the projects that you accomplish or don't accomplish, the impact or impression you made on each company, and the reason for the transitions.

Without knowing anything more: yes! But it depends on the reasons for leaving the jobs. If you explain it in your cv understandable it won't be a show stopper for your next application.

I would think so but usually when this happens there is some other reasons that can shed some light on this.

If you are working as a consultant, I really do not see it as an issue. There are always other "circumstances" that could lead to multiple jobs in three years.

It depends a lot on what field/industry you are in, whether they were consulting gigs, and much more.

Yes and no.
On first look, three job changes would suggest a job hopper. But in today's economy that is not the rule.
You have to take into consideration layoffs, company buyouts and a slowing economy.
In the last two years I have changed jobs three times in my industry and it has not been a problem.
By the way, I was laid off twice.

In general I think this is too many changes in a short time. But it does depend on why the moves were made. If there is a clear track of upward mobility then it may not be too bad. If these are largely lateral or just incremental changes then this is a little too much.

I believe yes, especially in Middle East area where I belong too. New careers been created/generated recently due booming business in ME. The main challenge is you need like a machine.

I think this largely depends on the job that you are changing from and to. For instance, moving from a Barista at Starbucks, to a clerical worker in an investment bank, and then from clerical work into a more specialized field of work, would be sensible.

Business requires a unique combination specialization and generalization. I think it is beneficial to address larger meta issues for a business after acquiring specific expertise. It takes a great deal of time and regular exposure to a large number of business specific issues to become an expert. As such, it does not seem probable that one could become an expert in three different areas of business, in three years.

Palm changed its logo three times in three years. So three job changes? I think not. Not anymore.