As a Englishman I'm used to just watching the sport in front of me and we don't resort to audience participation.
So what the hell is this? I know American sports have loads of delays and gaps but is this an accepted way of filling it up? I can think of a few reasons why you might not want to do this and this guy has brought up one of them.

Can't they just bring on a juggler or two?

Not sure quite exactly what you're referring to.

If you're talking about the fact that there's entertainment (i.e. the kiss-cam in question) it's because unlike most non-american sports, we have breaks in ours. Baseball has innings, so during the change between players at bat / players on the field, they'll go to a commercial break on t.v., but if you're actually in the park they typically try to bring out a "Quick Cleaning" crew to watch, or the mascot will dance or something

Same thing for football, except footballs entertainment is basically cheerleaders and the half time show.

Hockey, however, has 3 periods, at the end of each they bring out the Zamboni to clean the ice, making entertainment on the ice itself impossible, so they do things with the jumbo-cam, like the kiss-cam, to keep people entertained until the next period starts.

like football (soccer) isnt one big delay...

"American sports have loads of delays and gaps":

The Durban Test match (cricket) between South Africa and England was to be played as a timeless Test match and some eleven days later it was still left drawn since England had to begin their two-day rail journey back to their ship at Cape Town.
It still remains the longest ever first-class match of ten days of actual play. The match was abondoned (sic) as a draw after 43 hours 16 minutes of actual play.
*(from here)*

...Somehow, I think that a kiss cam or some other entertainment (sure, why not a juggler too?) would be a very welcome addition in a match like that. Eleven days, so 264 hours, with 43+ hours of active game play. Better make it a long list of entertainment!

It just seems hugely intrusive and presumptive. As a spectator I would feel irked.

*related=http://videosift.com/video/The-Easiest-Way-To-Avoid-The-Kiss-Cam

The Easiest Way To Avoid The Kiss Cam has been added as a related post - related requested by Zawash.