The psalmist knows a great deal of information about God, but more importantly are the indications that the psalmist has a strong relationship with God. To know about God and to have a trusting relationship with God are two very different things.
As persons concerned about the church as the people of God, this is the dilemma we sometimes face. I have a colleague who, once in while, with partial humor, quips, "I weep for future generations." I wonder how often school teachers say this in response to students who aren't excellent students of history, math, science, etc. The psalmist weeps because people do not know God, his Word, or have trusting relationships with God.
Are we like the psalmist who trusts the word, the laws, and the decrees of God so much that we treasure them in our souls? When they are lost or not kept, either by us or by our friends or by others, are we moved to tears on account of it? Simply put, the psalmist desires for all to seek and spend time with God.