Designed by Circle Design (now JTFDesign), they designed the iconic Plus symbol which is currently being used today (using different colors).
Also designed by Circle Design.
JTFDesign was again tasked to redesign the 2014 logo. The Font is now different, the B is now lowercase and the main colors are now yellow and grey. The Plus symbol is also lowered down. This logo was rolled out during the new June 3 update.