One of the reasons I'm a fan of walking in areas where my dogs can be offleash is this is much less an issue. I have a 'leave it' command when they are sniffing something that will maybe go next either into their mouth or get rolled on, but generally if they sniff for a bit it's not an issue.
That said, my dogs know the 'rules' on these walks. They have to be within sight and in front or beside me. If they are so into sniffing I catch up to them, it's a 'leave it' and move on. I have to be able to see them at all times.
When I walk on leash, if I'm just having them for a poop/pee I don't care so much for the sniffing either. BUT if we are seriously exercising, then we need to MOVE. So the sniffing has to be alot less cause we are moving out to get the cardio started for both of us!
Sniffing is an EXTREMELY normal behavior for our dogs and they get information from it we can't even imagine. I feel to not allow them would be similiar to almost taking away a sense like sight or hearing. Because I would be taking away alot of information they normally enjoy taking in. Makes them happy, so it makes me happy. And generally, in the scope of things in life, me having CONTROL ISSUES on an entire walk may need to take a back seat to the fact it's a normal and wonderful behavior for our dogs.
Hey, I'm going to start tracking classes cause I think it's so important for my dog!
Cool article about dogs and sniffing and how the NATURAL tendency for this is found in our dogs:
http://www.flockguard.org/trainbehaviorofdogs.htm (this may just be interesting and not help
)
ADDITIONALLY, sniffing is one of the 'calming signals' our dogs use all the time. One of the many things they do all the time to communcate with us (and we are too 'stupid' to get it) and they also use it to communicate with other dogs (and the socialized ones understand and get it right away).
http://dogbodylanguage.blogspot.com/
http://www.diamondsintheruff.com/calmingsignals.html