ET or not ET?

This is probably old news by now, but the SETI folks in Arecibo keep hearing something peculiar in the night sky. Nobody's getting really excited about it just yet, as the article does an excellent job of explaining. But there were a few chunks of it that made me scratch my head.

[The SETI project] uses programs running as screensavers on millions of personal computers worldwide to sift through signals picked up by the Arecibo telescope.

I've got this ridiculous image of the Arecibo telescope using the flying toaster screensaver to determine if ET is out there.

The fact that the signal continues to drift after this correction is "fishy", [Paul Horowitz] says. "If [the aliens] are so smart, they'll adjust their signal for their planet's motion."

This probably reveals my own ignorance about radio technology, but why would aliens just transmitting something for the benefit of their own civlization (such as, say, light rock of the Michael Bolton persuasion, or would that be something they'd procast to the detriment of their own civilization? that triggers a story idea...), would they be thinking at all about planetary motion? Do FM stations here on Earth do this? No matter the reality of radio tech, Mr. Horowitz's statement indicates that any signal we hear must be the result of ET trying to communicate with us. That seems to be a very odd assumption. Especially since our very first use of radio technology on this planet was all about communicating with folks not living on this planet, right? Sheesh.

The signal could be an artefact that, for some reason, always appears to be coming from the same point in the sky. The Arecibo telescope has a fixed dish reflector and scans the skies by changing the position of its receiver relative to the dish. When the receiver reaches a certain position, it might just be able to reflect waves from the ground onto the dish and then back to itself, making it seem as if the signal was coming from space.

The possibility that the telescope has a problem that could result in a signal from the ground looking like it came from space strikes me as something that really, really, really needs to be addressed by the SETI people before they go any further. Also, the physics that would allow such a thing are starting to give me a headache. Thus, I must sign off.