Varies by seller --- check the time frame over which they've been registered, and whether they have a huge post count of contributions to non-commercial threads. Some high-sellers have been here for many, many years, and are simply gearheads constantly churning through their own large equipment selection (a highly un-profitable enterprise). On the other hand, people who have only been here a year or two, and already racked up 100+ B&S transactions of new-in-box gear without ever posting outside their sale threads, probably have more commercial motivations. A high sale count alone is insufficient to tell much about the seller --- but you can combine this with their other posting/participation habits to deduce whether they actually use the wares they're moving.
+1 Exactly right, Sir. One (among several others) rule of thumb I generally use is to look at the dollar amount associated with the sale of each item as a function of the # of feedbacks - 300 Nikon battery sales for $35 is not the same as 2 sales of Leica lenses each worth $5250
Well I'm starting to get higher and high (i think 50ish right now), I just trade gear around a lot. I can't normally afford everything I want, so sometimes I have to swap gear and upgrade. I've always wondered myself if they just resell or are a distributor, I really dont care, as long as I get the lens I want at a price I like.
I can count on one hand the times I've "turned a profit" in 9 yrs here. What w/Shipping and PayPal fees...
even if I scored a great deal, eating those fees will usually put an end to that. I teach BIF and often outfit students,
as well as buy used gear for a fair sized network of local photographers. My stellar feedback and finger on the pulse
of the B&S here, instills confidence to try used and save some money. I'll usually get a beer or two for my efforts, but
the satisfaction of finding a camera or lens for someone...makes me feel kinda like a digital Johnny Appleseed. I also
am one to "buy n' try" gear for myself rather than rely on reviews etc., forming my own opinion for how/what I shoot.
When I used to spec. shoot, I'd buy a couple of bodies/lenses for a barrel racing series (18 weeks +/-) and a few rough
stock gigs and turn it when the season ended. Rinse/repeat the following year. I'm proud to be the only guy in the top 5
in feedback AND posts, here. I've earned my reputation...maybe that's why Fred still keeps me around?!
Holy crap Will, I just noticed you had 32K posts! I bow in honor to you
Regarding the buying and selling it does not bother me. As long as they are legit who cares? It is really only their loss if someone only participates in one of the forums.
My only issue with someone who is flipping gear is that they may not really know much about it's condition. I'd rather buy from someone who has used the item for months or years and can at least represent that it is in good working order.
While most flippers surely check out an item before they sell it that doesn't really compare to owning and using something for an extended period of time.
My guess is that many more people are flipping than most of us would expect.
As long as nobody is deceiving anyone, flipping is perfectly fair game IMO.
I've never done it with photo gear, but I've flipped items before that sellers were either undervaluing or not marketing properly.
If the person flipping the gear is being honest in the buying and selling process, I don't see why anyone should be concerned. The only issue is, as noted above, that flippers may not know the history of their gear - but again, that's part of "being honest." If I ask if they're the original owner, they need to tell me no. Then I will know they don't have the full history and can buy or not buy accordingly.
I can count on one hand the times I've "turned a profit" in 9 yrs here. 
What w/Shipping and PayPal fees...
I teach BIF and often outfit students,
I also