Android L Youtube API - IllegalArgumentException: Service Intent must be explicit
It is available a new version of the Youtube API (1.2.1) that fixes this issue. It can be downloaded from here.
If you need to use the old version for some reason keep reading:
There is a bug in the Youtube API v1.0.0 in Lollipop. More info here and here.
As a workaround you can use android:targetSdkVersion="19" in the manifest while maintaining API 21 as build target (You still will be able to make use of the Lollipop API in your project).
*UPDATE*
The new android youtube SDK has been released! No more implicit intent problem:
https://developers.google.com/youtube/android/player/downloads/
Just replace the old Youtube Api with Latest Youtube Api Version