As a person who had a really expensive bike stolen - I would never buy a bike from those places, I would not want to finance any criminal activity.
If you want to buy a cheap bike there are charities which sell them, and these bike will never be stolen since they are given to a charity for free, so why would you steal a bike to give it away for free? And they the charity fixes it up and sells it for 30-40 euros so they are cheap and reliable.
Don't understand me wrong. I understand that I support the crime that hurt me in the first place. I am not stupid but when I see how the Police gave up on that kind of crime, why should I still support it with new bikes? I rather support them with the small ammount of money instead and still have my mountainbike and am not that angry when it gets stolen again.
And I am pretty sure the police haven't given up on that crime, it's just easy to get away with it. When my bike was stolen a police officer came over and took the frame serial number,a picture of the bike and I do know they look around - I have been stopped on my bike before by the police who were looking for stolen bikes. It's just that those bikes can be easily packed on a truck and taken to another country,where no one will care, and there is no method to track a bike abroad, there should be a database with frame numbers that would be shared internationally.
Edit: And those charities are not just for poor people. The one where I live has all the bikes for sale arranged neatly in a shop, the only difference is that all of them have been donated, they fixed them and now they are selling them for reasonable amount of money to help people in need.
As I said, when a criminal act reached the point where the (possible) criminals advertise their goods openly (in newspapers, on the net, on flea markets), I think they just crossed the line. They a) seem to be sure to not be cauth and b) have already enough customers. So with my decision to not give them 100€ but "give" them a new bike worth 10-times that, I support their established market even more.
When I was ~15, I idioticly tried to sell a box full of my copied C64 games. I have been visited by some undercover cops who sued my parents for very much money. I never tried that again...
This is kind of a prisoners dilemma. You don't buy, others will, and you won't stop anyone, only hurt yourself financially. Problem must be solved in other ways, because "voting with your wallet" is not always effective way.
I can think of many situations where you could. And economic benefit often outweighs any ideology in places where people barely make it to the next paycheck.
Quit rationailzing your behavior -- either sin boldly or stop doing it.
Don't understand me wrong. I understand that I support the crime that hurt me in the first place. I am not stupid but when I see how the Police gave up on that kind of crime, why should I still support it with new bikes? I rather support them with the small ammount of money instead and still have my mountainbike and am not that angry when it gets stolen again.
Unless the stolen bikes you buy are in fact so cheap you can't have any possible doubt they are in fact stolen and you might as well steal them yourself.