Definitely an issue. I don't really like the idea of long-term Patreon-eseque relationship between the individual user and the attestor/issuer site, but it could be done. The charitable giving is more of a means-to-and-end than a goal, functioning as a kind of "observed spending" which is harder to fake than, say, buying something from yourself on ebay.

If tokens had to mature for X days before being used that could deter laundering pretty handily, but stopping "tests" of cards would require hiding payment errors from the user for a certain period... which would not be a great experience.