When I look through application resumes I've seen people who stick to big corps, some who move from corps to smaller indie scale operations, some who move from small to big, people who start their own companies than join corps, etc.
Honestly none of these particularly says "good" or "bad" to me. They don't even really make much of a difference barring a trend that is particularly odd. (but even then I give the candidate a chance to explain, it's pretty rare where they moved to / from bother me. Typically it's the Why and how that concern me.
What am I hiring for?
The biggest point I consider when looking at your work history is what sort of places did you work? What information can I find about them? Why did make your previous moves? Am I likely to be more like a company you'd move to or from?
These are all questions I ask when looking at your job changes.
Typically the things I watch for are trends, do you seem to move from companies that have a lot more structure to ones that allow for a lot more autonomy? if so would I fit in your trend, or would I be a reversal of that trend? Perhaps you moved from more traditional to more progressive companies, again, do I seem in line with your changes, or contrary to them?
Effectively if I spot a trend and I don't fit in it, that's not a black mark, but it's something I need to discuss with you to make sure you're a good fit and you'll be happy working for me.
What and why?
What you did for your previous employers is really important. Honestly outside of spotting people who are dishonest this is the single most important thing I find on your resume. It lets me know if you're past is related to what I'm hiring you for, where you work is only a special consideration if I know that employer and if they tend to hire good or bad people.
Why did you leave? This is the primary consideration I have in your job shifts in the past. Did you just get bored and move? Did you have issues with your peers? Are you just flipping to whomever will pay the most? What motivated you to change jobs?
There are MANY excellent reasons to change jobs that will put you on my good side, there are even more really terrible reasons to change jobs that will instantly put your application in my trash can.
What I'm looking for in asking about jobs past
I'm looking to establish two things when I look at / ask you about your past employers.
First, I'm trying to gauge you as an employee. Do you behave in a professional manner? Does your work history make sense? Is there any points of concern that need to be vetted? etc
Second, I'm trying to figure out what to expect should I hire you. How you leave past employers is practically a road map to how I should expect you to leave me. Did you just get bored? if so... would you just get bored here? Are you ambitious and needed to relocate to advance? if so... do I have advancement opportunities for you after I hire you?
Big to small, known to unknown, I only care if your reasons for the shift are in themselves a black mark.