I have to admit that I'm somewhat addicted to mapping power lines. :-)
Look at this map link, most of the lines there are from me:
osm.org/?lat=48.669&lon=9.4025&zoom=14&layers=B000FTF
(I have to use this in addition to the coordinate as you can neither specify the zoom level nor the renderer to be used.)

And this is no area where you can simply draw the lines on top of aerial images!
(This was possible to the West towards Stuttgart. The lines there were done mostly by other people and are complete.)

The station shown is *the* big distribution station in the region, about 20 km from my home.
If you follow the lines to the Northwest, you'll hit a black coal power plant as well.
So, lots of lines to map and as you can see I'm far from finished, especially if you count all the lines that run for kilometer after kilometer through the countryside to the East.
And after that, I can go up to the Schwäbische Alb and map until I reach Ulm as it seems nobody else is there who's interested in power lines as much as I am.
Well, you need a long term motivation for your hobby, right? ;-)

If you are interested in my technique:
I try to walk up to most power towers to set a proper waypoint. If I'm sure the line is running straight I use only a bearing from a nearby way to get the position of the tower. In OSM, I mark these with "source=interpolated".
I add the reference of the mast whenever possible. In Germany, this is usually a number for the line and a number for the tower, e.g. "Anlage 370, Mast 7". I do this to be able to verify which masts are still missing, even if they're obscured by obstacles or when returning weeks later. (The hard thing here is to make a sketch which includes these numbers before going out to the field. ;-) )
I won't go into the details of naming the lines, maybe I'll write about that later.

You might say: What's the point, it would make more sense if you spent your time mapping streets as that's much more useful for the rest of the community.
I thought about that and here are my reasons for not making more streets instead of power lines.
I know I don't have to justify myself but I want to share my thoughts anyway.
1) I don't get paid, so I do what's the most fun for me.
2) I've already mapped quite a lot of places and didn't stop with that either.
3) I end up in remote places where few people would end up so they wouldn't get mapped for a long time.
4) I'm also mapping streets and a lot of farm and forest tracks etc. when I map power lines. I just don't map the whole nearby village until it's finished. I've even done this for some like Denkendorf and Berkheim because I was motivated to fill in the street names and gaps there, I just won't do it for the whole region.