Internet is one great tool for everyone, so is for Music. Internet opened some new doors for promotion, and the people can express their support much better but the web is also covered of traps you have to avoid as for the sharing of your art through another webpage than yours.
From their support shown online, some people claim to be one promoter themselves while they are not in real. Some of them do it from their true support and aren't conscious how wrong they are doing it while some others know the consequences of their acts but don't care about. That last part may be another new shape of what some professionals would call "piracy" and those "promoters" think they are doing it fine since they write things like "no copyright infringement intended" even they ask to bands but they are just wrong.
Before to give your authorization for the sharing of your song, you have to care of the source, of the promoter's page, evidence and find infos about, ever. If you agree for the sharing of your art with your unsigned band, it’s up to you but if you agree while your band is signed at a label that knows well Intellectual Property while the promoter-amateur doesn't, then the art you authorized the publish by the promoter may be removed from his page by your label.
That problem happens often on websites like Youtube and others. Also, you have to know Google that is the Youtube’s owner now, has given to some labels video removal tools.
If your band signed or unsigned doesn’t own one account in the website, I advise to your band to create one, making it as the official page for the band and share its art itself through that website.
It will limit the closed links for copyrights issues and your songs will be always available for the people. Also, show to the people in the data from your new account that is the official page for the band.