Isn't it a bit selfish? I've had a few near misses over the last couple of weeks at Llandegla with errant dogs running under my wheels. The issues seems to be worse of a Wednesday evening when I guess people are combining a blast around Llandegla with their obligation to walk the dog. I'm not on about the shared access trails, I acknowledge that these are shared between cyclists, walkers, people with dogs etc.. and your speed should reflect that. I'm talking about the bike specific red and black trails where people are riding with their dogs off the lead with absolutely no consideration for other trail users.
Both last night and last Wednesday I had very near misses where a dog has shot out in front of my wheel and I have had to take evasive action to avoid hitting the thing, both occasions could have resulted in nasty injuries, to the dog and more importantly to me. Both occasions I was met with a casual "sorry mate". If I was unable to avoid hitting your dog, and ended up riding into it and hurting it, I wonder if the same casual "sorry mate" would be deemed a satisfactory response on my part.
I don't think dogs should be allowed on bike specific trails, especially ones where the owner knows cyclists will be carrying decent speed. Its irresponsible and selfish. Either leave your dog at home or if you need to ride with it do so somewhere more appropriate.