It seems that everyone who is vehemently opposed to tithing has a story to tell about how some pastor brow-beat them into tithing. I don't deny that these things happened, and I feel bad that they did. Offerings, in general, and tithing, in specific, are meant to be willing gifts given from a cheerful heart to God. Although many churches allocate the tithe to support the pastor, the tithe is given in honor of and belongs to God (several scriptures have been posted in this thread concerning this).
As to the actual record of the act of tithing, I have some interesting questions: did Jacob lie to God about tithing since no record is made of him fulfilling his vow? And if he did tithe to God, what possessions and increase did he include in his vow? Did he tithe according to the principles of the Order of Melchisedec or the principles that would eventually be established in the Levitical Law?
I believe that many actions and deeds are not recorded simply because there wouldn't be enough volumes to contain them. The diligent student is left then to decided whether those intents were actually followed through with.
Genesis 28:20-22
20 And Jacob vowed a vow, saying, If God will be with me, and will keep me in this way that I go, and will give me bread to eat, and raiment to put on,
21 So that I come again to my father's house in peace; then shall the LORD be my God:
22 And this stone, which I have set for a pillar, shall be God's house: and of all that thou shalt give me I will surely give the tenth unto thee.