Google maps has moved the "Add or Edit your business" link to the top of the details page. This is good news, because the link used to be at the bottom of the details page, and often below the fold...so it was rarely used.
Now that it is more prevalent, hopefully more business owners will Add or Edit their businesses using the Google Local Business Center. This is by far the most reliable and powerful method of correcting an error in your business listing. Now it's a bit easier to get there.
Google LatLong: A new world unfoldingGoogle now has an official blog just for Geo information, Google Lat-Long. Check it out.
One complaint often raised is that Google Maps shows lots of duplicates. Maybe yes, maybe no. Here's one I ran into today. Mid-America Industrial Park, Pryor, OK. At first, it appears there are four conflicting/duplicate listings.
But a closer look shows that, in fact, these are separate listings, just with similar names.
Location A is the office mail/delivery location, as given on their web site.
Location B is the "Main Office". Different phone #.
Location C is the actual location of the industrial park. Same phone # as A
Location D is the "Water Plant Division". Different phone #.
This is something you see frequently in Google Maps. It's clear that they would rather err on the side of showing more information, even if it often seems that the listings should be grouped together.
So, the lesson learned. Pay close attention to the listing title and phone number. It pays.
Using the basic Google.com web site brings Maps and Local listings
Usually I use the maps.google.com site for searching the map and for local business search. But you don't have to. Google has upgraded the ability of the basic Google.com website to find map locations and local business listings.
So here's how it works. You enter a query such as "60611" and Google interprets this (correctly) as a location, and gives you a map.
If you enter a business name, Google will interpret that as a "find businesses" search and give you a thumbnail map with three results. For example, "museums Indianapolis" gives you three choices. You can click on the map to get the full map display.
So next time you want to search for a map or a local business, give it a try on the basic Google.com. If that doesn't work, then go to maps.google.com where you have some refinement choices, especially in the "find businesses" section.
My business isn't listed on Google Maps. Why not? or... The information listed on my business on Google Maps is wrong. How do I fix it?
This must be one of the most common questions asked by business owners. Here are some answers!
1. Take charge of your listing. Take ownership of what Google Maps displays. Go to the Google Local Business Center and register your business. Verification is required. Use the telephone verification method, if it is available. (Google will show you a PIN on the PC, then they'll call your number, and 
you enter the PIN. Takes 20 sec.). This is by far the easiest method. It's free, and you do not have to buy Google Ads. AND it will overwrite whatever Google Maps is currently showing. If it's a new business, you'll see the changes right away. If it's an update to an existing business, that can take 3-4 weeks.
2. On the "more info" page, at the bottom is a link that says "Business Owners: Add/Edit Your Business" and a link to the LBC above. Most people don't know this link is here, probably because it is often below the fold on the page. Google really should make this link more prominent. 
3. Finally, if you still can't get your business corrected. Leave me a comment, and I'll try to help. I bet you won't find that statement on any other Google Maps blog!
Here's what does not work...sending an email flame to Google, writing a nasty letter to Larry Page, or having your attorney threaten to sue Google. Google Maps gets its data from public sources such as web pages and other public data sources, i.e. 411 service. If you really have a problem with your 411 listing, it's not Google's fault. Call the 411 service.
