A sommelier is a trained expert on everything to do with wine. They are extremely knowledgeable individuals that understand all aspects of taste and how these tastes will pair with an entire menu of food. Among other things, a sommelier might build a wine list for a restaurant, create suggestions for wines that complement particular foods and assign wine ratings.
Any person who has a great deal of expertise on wine can become a certified sommelier but only a small number of individuals can claim the title of Master Sommelier. Master Sommeliers have gone through years of rigorous training and these individuals can claim the right as masters of their trade.
Just as the case with a sommelier, any person with a great deal of expertise in printing can become a certified commercial printer however only a small number of printers can claim the title of master. Master certification in the printing industry is conducted by IDEAlliance and G7 Master & Expert certifications are given to those small few who can prove they are masters of the print trade.
G7 Master Printers are able to ensure the highest level of color match consistency from proofing to printing. This standard means the company uses the most modern technology and techniques as it applies to proofing, printing and color calibration controls. G7 Experts are individuals that are deemed as master specialists in color management, proofing, plate making and printing of all varieties. To put it simply, a G7 certificate deems you an expert on all things color as it relates to printing.
Does this mean that non-G7 printers aren't good at color management? Absolutely not as many printers have a number of practices and procedures in place to ensure their proofs match what prints and that color remains consistent from press to press. You can still rely on the expertise of a non-G7 certified printer as after all, this is what they do for a living! In addition, there are numerous other certifications available that prove a printer has high-quality control standards.
I am still of the belief that the most successful printers will always be the ones that place the client first, care and are passionate about the work they do (master certified or not). It's just like walking into an established wine store and seeking out the expertise of the owner. It's highly unlikely they are a Master Sommelier but these people have the knowledge and resources to guide you into a purchase you'll be happy with to ensure you return in the future. However, there is something to be said for the printer that takes the time to go through the certification process to prove they are masters of their trade.
Related Links and References:
Guild of Sommeliers
International Sommelier Guild
Court of Master Sommeliers
Sommelier Facts on Wikipedia
G7: What is it - and Why Should Print Customers Care?