Scams, scams scams
Let me tell you upfront - anyone who promises to give you a multiplier of the coins you send them. no matter how genuine it looks, is a scammer.
What I believe they have done is hacked Brad Garlinghouse's Twitter account so when you see the scam post it looks like it's come from Brad Garlinghouse.
Brad Garlinghouse (The real one) posted this tweet some time ago:

There are a heap of these scam artists.
"Send XRP to this ripple wallet and Ripple will send you 10x the amount back!"
"I'm giving away X number of XRP to one lucky winner. All you have to do is subscribe and share this post"
"I'm raffling off X number of XRP to one lucky winner"
No-one is giving away XRP. Fullstop. Period. End of story". These are hackers/scammers who will hack your account and/or steal your XRP.
Here are some sample tweets;

and another one ...

Please don't fall for these scams. When you do come across them, please report them to help protect the XRP (and all Crypto) community.