I always stop to help out a fellow rider on the side of the road. In the last couple of months I have helped out several riders who needed assistance.
Case 1. Was on my way to a tech session for KLR riders in Calgary when I happened upon a guy sitting on a sportbike up against the concrete median in the middle of the Deerfoot (innercity freeway). Turns out he had fuel, but his bike wouldn't run without full choke, and even then it had no power. Followed him for a little ways after we got him running again, then when it was apparent that his bike wasn't going to get him home, I gave him a ride across the city (was actually on my way) to meet his friend so they could get a truck.
Case 2. Was pulling out of a Tim Horton's in Red Deer last week and there was a guy with a Harley pulled to the side of the turning lane with his bike in pieces. I didn't have my bike (in the process of fixing it) so I didn't have my full toolkit, but I did have my Leatherman with me. His battery cables had both broken, so with some creative use of my leatherman and some electrical tape, I got him up and running again so he could get home for a proper fix.
Case 3. Was heading home yesterday after taking my (newly fixed) bike out for a spin when I stopped for an older couple on the side of the highway standing next to their BMW. They were ok, they'd just run out of gas. I offered to head home and get my 5L jerrycan for them, but they already had AMA assistance on the way. I stayed with them and chatted until the tow truck showed up with fuel for them.
Case 4. Stopped for a guy on the side of the highway on my way to work this morning for a guy with an older Kawi. Turns out he'd run out of fuel, but he was alright as his friend was about 30 seconds behind me with fuel for him.
Case 5. I was out playing around in the dirt one sunny day and there were three other guys with dirtbikes out having some fun as well. None of them had their tools with them, and the one guy (with the Honda) had a few critical bolts coming loose, so I pulled out my toolkit and got him fixed up and back running safely so he could enjoy the day.
I firmly believe in stopping to see if a rider on the side of the road needs assistance, whether I'm on my bike or in my car. I would appreciate it if the situation were reversed and I was the one who needed assistance. In the case of the guy with the Harley, he remarked that he had seen at least a dozen other Harleys go by while he was stranded there, and not one of them even bothered to look (friends of Moto, perhaps?).
I have stopped a countless time for bike but none for other cars or hitchhiking. I have stopped no matter I'm in the car or on the bike. I also have seen ppl do the same as well.
