Have sponsorships on YouTube gone a bit overboard?
...yes. The answer is just yes.

Music:
Metallic Madness Bad Future - Sonic CD
Windows XP Tour 2 - Bill Brown*
Windows XP Tour 5 - Bill Brown*
Current Capers (Aquatic Ambience Returns) - DKC Tropical Freeze
Hard Technology Rock - Half-Life
Bowser Battle - Mario & Luigi: Partners in Time
Windows XP Tour 6 - Bill Brown*
Robot Waiting Room 4 - Portal 2
Electric Guitar Ambience - Half-Life
Forest Interlude - DKC2
*Depending on where you find these music tracks, you'll find different track titles or even track numbers. These are based on the track titles as they are shown on the creator's soundcloud

Additional credits:
James Rolfe sponsor segments from Cinemassacre -    / @jamesnintendonerd  
Tom Scott's video on VPN sponsorships -    • This Video Is Sponsored By ███ VPN  
Tom Scott's robot video -    • My robot double sells out (so I don't...  
Max G's Brain Dump Episode -    • What Is Fash Ism?  
Civvie's video -    • Half-Life - A Linear Sequence of Scares