More plausible ...
http://www.news.com.au/couriermail/story/0,23739,24084861-27197,00.html
Another interview, here:
http://dsc.discovery.com/space/qa/al...-mitchell.html
Before his stories broke on the news, the topic came up on another forum. Someone's point of view was, that any civilization capable of traveling interstellar distances would put enough redundancy into their designs that, if avoiding detection was their aim, they would succeed. The conclusion of this person was, either we'd never see the alien craft or we'd have seen several. But our manipulating circumstances, so the we catch a semi-hazy glimpse of one, or they make a sloppy landing that leaves a little, dubious, evidence was running counter to why they'd visit in secret at all.