On the etymology of "sucks"

Thanks for the info! Here is the link to the other thread, which provides more useful commentary:
http://boards.straightdope.com/sdmb/showthread.php?t=803542

That thread has a comment:

This is more or less consistent with my recollection. I remember the expression “you suck!” and “this sucks!” as a new expression sometime in the early 70s. It definitely had a sexual implication, as I remember it.

Also from that other thread:

That is also consistent with my experience. I’ve found it interesting to see how, over these many years, the expression has sort of lost its naughty sexual implications and become more acceptable in the mass media and in the mouths of politicians. But it took a long, long time to get there.