What is the key purpose of a Business Card and has this changed?

I have a collection of business cards with some that are decades old. You may have a stack too, a collection from a recent event, a meet up, conference or convention.
Each business card is different if you go through them some you keep others you may toss. Those you keep it is likely all contain similar elements and have readability. This means the typeset words can be easily and quickly read.

Today many methods exist to contact a person. Arguments abound on what kind information is best or important to include on a business card. Some argue a P.O. Box is bad to use for an address. Card design exist with the entire card crammed with information, from Facebook, linkedin, Skype,  the card can end up looking like a newspaper article.

Here is my take on the Key Purpose of a Business Card

1. Conveys Contact Information
Above all else, a business card is a tangible object that’s used to provide your contact information to potential customers. Because of this, most business cards contain your name and title, your telephone number, an email address. Other key information includes; the business name, and a street address, a office phone too is ok especially if you have a reception desk to answer. Your company has a website, so included the URL address so that customers can receive more detailed information through it. A fax number only if you and customers use it weekly. When was the last time you sent or received a fax? The company logo is ok, it needs to be a balanced part of the card design. That means it is a small design element.

2. Helps Customers Remember You
While a business card conveys the means for customers to be in touch with you, a business card also serves as a way for customers and colleagues to remember you after a first meeting. Different strategies and practices are used. Some like to go with a lines or completely blank back, so that you or recipient can make a note on the card back. Sometime the business card has a unique or catchy tag line on the card back to jog customers’ memories about the circumstances of their meeting. These strategy can be a mnemonic tool to help customers recall meeting you, then merely by the name on the card, your handshake and smile.

3. Reflects Your Company's Values
A business card is a piece of your company’s marketing plan, albeit a small one, so it should work with existing materials, such as letterhead and envelopes and other supporting marketing communications collateral. A card is designed to convey the spirit of your company’s culture. Consistency is good, the same logo, company typeface, company colors are applied across visual media. The correct paper card stock is used, matching on stationery items . All materials should look related, seem to be a set.

4. Differentiates You From Competition
It’s almost a given that your customers receive several business cards from your competitors. A consistent look of all marketing communication collateral, including stationery and your smartly designed business card helps your company stand out among the crowd. Some entrepreneurs choose to use die cuts to create unusual shapes for their card, while others use perforations, folds and pop-ups to differentiate themselves. You don’t need to resort to gimmicks; a concise, direct and visually appealing and readable card that projects your company’s identity is as effective in differentiating a company as a novelty card.