All animals are equal

Don't Gag your Chickens!

One of the main components of agile development taken
from the Scrum methodology is the daily stand-up meeting.

The meetings are meant to be a way to get a quick view on the
development status. The usual idea is for each developer ("pigs")
to say what they did yesterday, what they're going to do today,
and what obstacles do they have?

They are supposed to last for at most 15 minutes, and while
non-developers /product owners ("chickens") can be invited,
they are not supposed to talk. The main rationale for not
allowing them to speak appears to be to prevent "scope creep".

While there are some dangers in allowing product owners to
participate in what is mainly a developer status meeting,
I've also found that there are many advantages that clearly
outweigh those risks when the meeting is properly run.

It's been very useful to have a product owner there to remove
roadblocks - many of which can either be removed by getting an
answer to a simple question, or just by reminding the product
owner of something they need to do. The product owners also
find it useful - being able to tell us of any concerns they have,
help us set priorities, or just to ask more specific questions
on the status of something.

The concern over the meeting lasting too long is just immaterial,
We all waste plenty of time at work during every day. If a
stand-up meeting occasionally takes 5, 10, or even 15 minutes
longer because product owners are participating and it helps the
development process, that's time that's very well spent.

Preventing product owners from fully participating is just
adhering blindly to a strict methodology. That's not what the
heart of agile development is about. As long as you're able to
control the meetings so that scope creep does not set in, and
the meetings don't get out of hand, then having that daily
two-way communication between the development team and the
product team can be extremely valuable.

Do what's right for your team. If your product owners add value
by participating in your daily standup meetings (and your
developers and product owners agree), then that's the right thing
for your organization. If you find that having them there but not
allowed to speak works better for you, then that's what you should
do. But you shouldn't do something just because someone tells
you to do it.

Only you know what works best for you and your company.