the only thing im aware of ... is they can transfer bacterial infection from tank to tank.. (from one unhealthy anemone to another healthy anemone...)
ive delt with it in personal experiences... where I had an established anemone, and put a new un-quarantined anemone right into the display tank and saw both go threw the inflate/deflate cycle... and both ended up dead... (when I was a newer reefer and less experienced.)