First, what is it's purpose?

Well, the purpose of Hive account@bumper is to support the subscription service Hive account@moonbot. Subscribers of Hive account@moonbot who want higher payouts on their posts send 0.5 SBD (or the equivalent in Steem because these SBD prices are crazy!) and they get double what they put in (ex. Curation) and all profits of Hive account@bumper go towards making Hive account@moonbot a better and more well paying service for it's subscribers!

Why is @Bumper supporting @Moonbot?

MoonBot is a very expensive bot to run due to the Unlimited Upvotes it provides its subscribers for 30 days. So in a nutshell; MoonBot - Expensive, Bumper - Make money for MoonBot.

Why should I use Hive account@bumper over MinnowBooster

Bumper is the only service that Guarantees to double your investment at minimum. with 200% Expected ROI. It's a clear win : )

What are some downsides to Hive account@bumper ?

Bumper is no where near as fast as other bots like MinnowBooster as all the votes are done manually to ensure that you get your return of 200% and votes may be delayed to allow Hive account@bumper time to recharge it's Steem Power. But all of this is to make sure that you receive your 200% ROI