Loyalty - Old Fashioned or Still Current?

I took part in a lively discussion today about loyalty.  One person, who seemed to equating loyalty with hakaras ha'tov (gratitude), maintained that although people will say it's a valuable trait, it is nevertheless, quite a rare commodity these days. 

Someone else said that loyalty is highly regarded in her family.  To illustrate, an aunt in Russia in her teens, without parents and having the opportunity to leave communist Russia, remained there for the next thirty years.  Why? Because her brother had been wounded and who would take care of him? If he couldn't walk, she needed to be there for him! This wasn't about hakaras ha'tov; it was about family sticks together and I stand by you, no matter what. 

Someone called that devotion and tossed in the idea that Rabbi Avigdor Miller z'l said that marriage is not about romance; it is about loyalty and devotion.

This led to a discussion about patronizing family members and friends when you need services that they provide.  Although supporting family and friends is an act of loyalty, it is also a potential minefield.  Stories abound about fallings-out, disappointments and unhappiness when doing business with friends and relatives.  Some maintain that business and friendship should remain separate.  The counter-argument presented today was, if you don't support a friend in business, then how are you a friend?

A related question, are we loyal customers or do we shop wherever it's cheaper? Do I have a halachic obligation to be a loyal customer? What about a halachic obligation to be loyal to family? The mitzva of "not ignoring your own flesh [and blood]" comes to mind.

And if loyalty is faithfulness, then an example in the Torah is Moshe whom Hashem describes as being faithful, ne'eman to Him.  Another Torah source for loyalty-devotion-faithfulness is the reason only certain kinds of birds (the tor and the bnei yona) are brought as sacrifices; because they exhibit loyalty and faithfulness.  Any other sources?