My take is the following: There are no con's for bike lanes! :-)
Really I meanThink of it.: Are there discussions of pro's and con's of sidewalks (aka pedestrian lanes)? No! Why? Because of course it isthey are useful! We have to protectIt's a matter of protecting the fragile against the one ton metal boxes that are propelled at 50km/h!
However, there are many con's for how local politics have decided to implements bike lanes because they fail the purpose of it: there are inconsistencies, they are not enough separated from the road, they are placed dangerously, etc. Each time we witness such mistakes which should contact our local council and tell them about it. OK, I agree, it's not always useful, where I live they don't listen at all. But that's why there is elections, and I vote where my mouth is!
In Toulouse, bike lanes are nice but improperly done in most cases. They can even lead you to a one way street with no bike lane and you will be against the traffic (rue A. Dauménil)! Or they share part of the sidewalks leaving no room for pedestrians (allée M. Sarraut). Or they share the road (just a bit of paint) and suddenly the road gets narrow and you get squeeze between a car and a high sidewalk (avenue C. Pujol), which means you are in danger! So yes, bike lanes in Toulouse have lots of con's, I just hope they will do a better job at it.