It is nice to just not worry about piracy, and that is right for most indie developers. There isn't much more you can really do anyway. However, not all games can easily make use of online added value (SingSong). In this case I would (and did) opt for some simplistic mechanism to make piracy more difficult.
It's more about a point of diminishing returns. Beyond simple measures it just costs more than it is worth to put DRM in software. The last example was Ubisoft puting in a DRM that would require you be online at all times to play. Well their paying customers played the game less than the pirates since they had problems with the DRM server and clients on WiFi would be kicked off every time the connection cycled. Meanwhile the DRM was broken within a week.