Prior to the latest "upgrade" I was able to send local coords to Maps (via http) and Google would place a marker on the exact spot (within about 10') WHILE navigation services remained active - i.e. a user could navigate to the very spot.
Now, as the above poster notes, that capability is gone, which trashed about 2 months work for me. GM will still mark locations, but not with navigation. If you try, your location will be the nearest business. (?!!) Hate to sound cynical, but, based on the reaction in forums, it seems like Google couldn't have done a better job wiping out hundreds of small enterprises with a single swipe, had they planned it!