Ok, this is a great one because it's both pervasive and controversial.  Starseed is one of the most out there occult-identities listed on the Wiki, and it's not uncommon to find a couple of them on a given Otherkin forum.  Most people are relatively respectful to them, but the more scientifically based thinkers tend to be extremely skeptical of them.

I remember the first time I came across them: it was in a thread on some wacky Otherkin board.  One of them had drawn a simple diagram of the earth, his origin planet, the inter-stellar-astral-passage he'd been sent along, and the mothership which was coming to earth.  I'm pretty sure I burst out laughing at how silly this was, and said some stupid things about how silly it was, to which the forum members responded that "this is all standard stuff" and "The mothership has been on its way for quite some time".  (I ended up getting banned from that forum, but that was years and years ago, and is neither here nor there)

Now, I don't try and tell anyone what beliefs are ok to hold: whatever keeps the boat afloat works.  I will say though that it is a massive leap, even from therianthropy, to believe that someone has been spiritually sent here by an alien race as part of some overbearing "mission".  It's not that big of a leap to believe that aliens exist on other planets, or that this astral stuff exists, or that aliens on other planets are involved in that.  The leap is to believe that another, alien race, has developed astral-soul-catapults to send members of their race to our planet, and that you specifically got here from that.  The idea is interesting to ponder, but it's quite grandiose.

Now, this isn't to say that I haven't met some very down-to-earth Starseeds (no pun intended), but I do think the idea in itself tends to come with alot of silliness and overly-magical thinking, or worse, escapism.  I would hope that anyone who believes this would take a very careful, through look at why they believe this and how they act on it.

And that's me for now on Starseeds.

Coming off of what I just said to Random over Skype:

When I really think about it, Starseeds aren't so weird.  When you factor in the fact that some people think that therianthropy is a reincarnation thing, and that some of those people believe in weird soul-rotation setups and "higher purposes", the idea that some of those souls in the rotation are purposefully sent from other planets isn't that far a leap.  Also, angel/demon kin are out there too, and quite a few of them talk about a sort of celestial hierarchy that their souls are part of.  So if you're into the wacky spiritual stuff, it's not a hard thing to believe in...

Random thinks it sounds like Scientology though.

...A bit off topic, but ok...