Yes, it's important to remember that the seemingly "perfect" couple PDA-ing away on the street could be done like dinner within the month...or else their relationship could drag on in pain and agony for years.

We tend to project our own assumptions when we see things that hurt us...perfectly natural (btw I did laugh when you said you throw things are such people, but you really shouldn't do that...you could get in a lot of trouble, and acting out one's anger is never the way to go to help yourself, which is the important thing).

As for PDAs, I tend to put the people involved in two categories: those who are too swept in their newfound love to realize that they are offending and annoying others, and those that PDA as much as possible to "show off" their relationship. As for the latter category, I can guarantee you that most of those relationships won't last...people who need to show off how "in love" they are to others usually have a more superficial relationship than they realize, and then will come back on them in the end.