Here in the Netherlands, low powered motorbikes called bromfietsen are allowed to use rural cycle paths. These include many of the cycle paths on which I commute. In the middle of the countryside they're allowed, while at each village along the way they are sent back onto the road.
These things can be a minor irritation, but it's actually quite advantageous to faster cyclists that these bikes also use the cycle paths. It means that the cycle paths have to be designed to be suitable for speeds of 45 km/h - the legal limit for these bikes.
They also provide a bit of sport. On a good day, I overtake them:
This is the opposite side of the road from the photo above. There's a unidrectional 2.5 m wide cycle path on both sides of this road. This video must be played on a computer and not a mobile device if you want to be able to read the textual captions
May 2011 update. Amusingly, the Guardian (who normally ignore me) linked to this post and seem to have taken it a bit out of context. There is really no similarity at all between the wide rural cycle path I show in this post and urban cycle lanes in the UK.
"Brommers" limited to 45 km/h are also rather different to "motorbikes" in the UK. I should also point out that here in the Netherlands, these brommers are a nuisance sometimes, when ridden irresponsibly in the wrong place at the wrong time. . However, they're not really a major hazard. This is also covered on this blog.
Lastly, people cycle in the Netherlands far more than in any other country. If you want to know what makes this possible, click here. For a list of reasons why you might think it's impossible for this to happen in the UK, and why they are wrong, click here.
There are also posts about The Guardian, which often looks in the wrong direction where cycling is concerned.