A few users and customers have said how they like how bliss runs in the background:
[bliss] grabs album covers for your music collection, and it does it automatically, it does it in the background, it does it with a Web interface and it's very cool if you happen to run a Squeezebox or keep your music collection on a large hard drive. I think it's a great tool. [...] The user interface through the Web GUI is great. If you want album art, it's the best way of getting it.Graham Morrison, Tux Radar podcast season 2 episode 3
This is a big difference between bliss and other album art and music management tools. Most digital music users are familiar with using taggers to organise their music. Once you close the tagger user interface, the software stops working. bliss works independently and its user interface is accessed via a Web browser like Internet Explorer, Firefox, Safari or Chrome. You can even access the UI on an iPad or iPhone. Close the browser, and bliss keeps on managing your music.
There are a few reasons for doing it this way.
So that is why bliss runs in the background.