there's a trend for group 14 elements; they are all able to form many compounds, but as you go down, they form less compounds. the reason carbon is so versatile is because it has 4 valence electrons, and thus can form 4 bonds and perhaps more, depending on if something is to create coordinate covalent bonds, although carbocations are extremely unstable and only can exist for long periods of time (more than 1/100 second) when in a solution of 50% HF:SbF5
C forms "nets". ever notice how graphite and diamond are both pure carbon? what makes them different is their structure. they form large patterns.