I've been in well run Agile teams - and they're wonderful. I've been in badly run "Agile" teams and they're soul destroying. Either way agile is not the problem (or, I dare say, the solution).
I can see that the motivation is to avoid wasting the whole team's time on a discussion that only needs two or three people; but suppressing discussion can hurt too, as it stops people learning about tricky issues outside of their immediate work area.
It would be helpful to have some rules of thumb to show when you're doing Agile wrong. Probably those exist already -- anyone got a good link? And probably "too many people in the standup meeting" is a good rule of thumb!
Dragging on for an hour sounds absolutely awful. I'd even say more than about six people is too many.
I had one team of 10 that had a problem with our standups extending into half an hour once. We resolved that we'd make the standup one minute shorter each day. After a month and a half, we had it down to a one-minute standup (6 seconds per person). It was still useful, though a bit extreme - I'd target about 5 minutes for a 10-person standup (30 seconds per).
But we had a real agile guru on the team. We didn't do "Agile Methodology" exactly; we did Extreme Programming, and we kept tweaking it. Sometimes he'd say "let's try changing our approach in this way for the next two iterations, and see how it works out". We'd do the experiment, and keep the changes or not. We kept hacking and experimenting with the process, in a controlled way, but never in a "this is how it's done" way.
So if you have an "Agile is the one right way" person trying to run your team with big-A Agile, and he/she wants to do 30-person standups, you're probably in trouble...