Dumping Stellar coins should be prevented for at least five years provided the creators adhere to the agreement described in their Mandate page:
"In order to provide additional stability to the system, the nonprofit founders and Stripe have voluntarily agreed not sell any of the stellars initially received (either via employee grants in the case of the founders or via repayment of the loan) for at least five years; however, Stripe may auction any of their stellars, provided the recipients also agree not to sell their stellars for five years, and net profits are returned to the Foundation."[1]
"In order to provide additional stability to the system, the nonprofit founders and Stripe have voluntarily agreed not sell any of the stellars initially received (either via employee grants in the case of the founders or via repayment of the loan) for at least five years; however, Stripe may auction any of their stellars, provided the recipients also agree not to sell their stellars for five years, and net profits are returned to the Foundation."[1]
[1] https://www.stellar.org/about/mandate/#Stellar_distribution