Well, as I already mentioned, in Austria we are not allowed to cycle on the sidewalk. But we have bike paths (one-way or both ways) on sidewalks. And there are also a lot of so-called "combined foot and bike paths" that are for both pedestrians and cyclists (either separated by a line or not). And some of this constructions are just as dangerous as cycling on sidewalks. Unfortunately I'm forced to use them (if one has a road bike s/he doesn't have to cycle there, but I don't have one). Sometimes they are an advantage, e.g. if it is a short cut that I couldn't use otherwise, but they are a huge disadvantage and risk if they are just built to keep the road bicycle-free.
Combined foot and bike paths: The left picture clearly shows a short cut. One has to ride slow and watch out for pedestrians, but it might be an advantage. It's in Linz, where many combined foot and bike paths exist. The right picture shows a combined foot and bike path in Vienna (just the little bit where my bike stands). What you don't see is that cars have 4 lanes in each direction! And cyclists have to share a space with pedestrians that's even so small, that two pedestrians can't get by very well. The tragedy about it: due to our traffic regulations I have to use this combined foot and bike path and can't cycle on the car lanes! And this is an arterial road in the middle of Vienna (Gürtel at Volksoper, for those who know it). It's a real shame to call something like that a bike path and add it to the ~1000km of bike lanes in Vienna that the city council is so proud of. I don't know who plans bike paths like this, but it surely wasn't a cyclist.
A lot of accidents between cyclists and cars/trucks in the city happen on bike paths and bike path crossings because cyclists are not visible to car drivers there, but still feel safe (although they aren't). In addition, most car drivers don't shoulder check, what makes it even more risky. For truck drivers it's even more difficult to see you since they can only use their mirrors - never ever stop right beside a truck at an intersection! Last year many cyclists have died this way - overran by a turning secondary car/truck on a bike path (crossing).
Don't get me wrong. I do like bike paths out of the town, but generally not in the town itself because there are way to many dangerous junctions. Ok, it's not a natural law that they are dangerous, but due to bad traffic planning, dense housing and illegal parking a lot of them are. In the city I prefer sufficiently wide (!) bike lanes on the road because there I'm visible to car drivers and much safer. Or even better, low speed limits and many restricted areas (30 km/h zones, residential streets and such) with no bike lanes at all. And a few bike paths beside busy and important roads with a lot of (heavy) motor traffic. Appropriate bicycle infrastructure meets the hierarchy of the road.
Another bad example of a bike path in both (!) directions. How small might it be? 1-1.2 meters? Do you think that two cyclists can pass each other? Compare it to the car lanes next to it and form an opinion yourself. There are 4 of them in each direction - the location is close to the previous picture. At this particular spot you can even see 5 lanes. Well, space has to be saved somewhere, doesn't it? I just don't get why they built a bike path there in the first place. To get the road bicycle-free I suppose.. Also note that cyclists and turning car drivers have to be really careful at this bike path crossing to not interfere with each other. Such designs bear extra potential for conflicts rather than avoiding them.
If you want to see some good examples of bike paths you must go to Copenhagen or Amsterdam etc. Maybe I sound a little bit to pessimistic - but in Vienna there are hardly any. But ok, I will take some pictures of well-designed bicycle infrastructure in the future too, I promise ;-).