Kanye - Dating Kim Kardashian (and Knocking her up tbh)
Natalia Kills - Not promoting Mirrors enough or not releasing Problem by now
Lana Del Rey - SNL performance
The xx - Baria leaving the group
No Doubt - Taking so long to reunite and failing to properly promote singles from P&S
Rihanna - Releasing an album in Nov 2011 (Should've waited for at least May '12)
The Weeknd - Echoes of Silence
Dev - Delaying her album in the US for 'new songs', when we only got 2
Lady Gaga - Interesting one.... Not releasing Marry The Night as the first single from btw. I think it would have made the era overall more successful since the title track would've been a #1 hit no matter when it was released