I'm experienced enough to not get many what I would call 'real' bugs in my applications, of course there are a few. In general these now seem to come in a two classes.

1) What I would call process bugs come from a scenario like user X presses shift tab in field Y and then presses enter before completing the date in field Z, which no-one had tried out in testing and it breaks some validation - perhaps in a particular browser.

2) Data related bugs where if particular (unexepected) values are entered or uploaded then maybe a divide by zero or something can occur - it seems hard to prevent this possibility however much you think things through and how much you test.

If it does not work how the user expects or wants I call that a problem (or 'solution staring point' in one of my past employers client facing patter!) rather than a bug. However I would agree that bug fixing has changed significantly since I started programming - perhaps doubly so since I do not really do Winforms work much these days, with fairly different problems to the web.