To everyone who has gone down the "oh my god, these are WEBCOMIC CHARACTERS you're debating, people!" route - I'd like to point out that yes, yes they are. Characters that, as far as I can tell, are intended to be realistic and for that reason, I don't see the slightest problem in attempting to psycho-analyse any of the occurrings. If the plot stopped being realistic, QC would experience a dramatic drop in quality that could not be excused by saying "well, they're webcomic characters".
I am not saying I am nuts and fully expect the characters to have a mind of their own out of Jeph's control - no, he is obviously the one writing the plot and the character's actions, but unless we are able to trace the justifications behind them, then the storyline becomes useless. Good character development is a mark of good storytelling. Simple.
I've seen Sven/Faye coming for a long time. Of course, there was always the "No, Jeph would not do this as it's TOO obvious" aspect, but I am pleased it did. I daresay it NOT happening would have been unrealistic if the friendship had continued as it has. The only other alternative would have been for Faye to distance herself once again (not neccessarily because of any romantic feelings per se, but just down to mere 'he's not such a bad guy' sentiments), and nobody would have liked to see that happening.
Sven was a likely candidate - BECAUSE he embodies so many things Faye dislikes, it would have been easy for Faye to initially feel secure in the knowledge that NO, nothing would ever happen between them. That's one wall overcome, which might explain how she became so friendly and comfortable around him. Which then in turn more or less naturally would have led to sexual tension simply because Faye is the sort of girl Sven would not go for and vice versa, and yet here they are, getting along (more or less) well, keeping each other nice and grounded.
We must also not forget that presumably, they had been drinking a little, and yes, alcohol lowers boundaries. There was one stopping point just after the first kiss, but anyone who has been in a similar situation should be aware that stepping back then is an extremely unlikely course of action. Though again, Jeph could have stopped there and had her freak out then and nobody would have really questioned it. Instead, it went further. I'm currently enjoying the inevitable post-coital-bliss Faye must be experiencing (I see her madly bouncing around CoD and putting it all down to the caffeine).
Where to now? I don't see this becoming something romantic. Not for the time being, anyway. Neither of them really have the personalities or are at a point in life where "let's give a relationship a try" seems like a realistic thing to say or even consider. Faye could freak out completely... but that would, I daresay, annoy most readers. As far as I can see, she has been on an upwards slope in recent strips, and I doubt sleeping with Sven would throw her back down. Dopamine, kids.
"Pushing boundaries" may indeed be the keywords here - I almost see it as Faye taking advantage of Sven. He wouldn't have said no. Pushing her boundaries with him was, relatively speaking (in comparison to other guys) easy. What, to me, remains to be seen is whether it's a repeat occurrence or whether they leave it at that and never speak of it again.
Things that have entertainment potential:
-Sven telling Dora what happened. He might just do so out of fear that Faye will do so first, in a not-so positive light. (Incidentally, Sven, casually as he is acting now, may suddenly go into a sort of guilt-trip mode).
-Hannelore, traumatized, refusing to talk to Faye. She may turn to Pintsize/Wainslow for advice. Pr0n attack engineered by the former ensues.
....and of course, I am personally just waiting for the line "Well, yes, we were making out, but you were so drunk you just kind of fell asleep before we actually got down to the sex."
((PS: I may have gone a little overboard with this length-wise. Apologies.))