You all have very good points and in my opinion, there are no hard rules in making chord progressions. There are however something like standards that are being used and have been used for many, many years in something like 98% of pop songs(btw, that was a made up percentage, but you get my meaning).
Another thing to consider is the timing and rhythm of chord changes, you could be using "standard" chord changes like G-C-D-G, you could, instead of having each chord last for 2 or 4 counts or beats, use different timing of the chord changes, say having the G last for 4 beats, the C for 5 beats, the D for 3 beats and the last G for 4 beats.
I hope you catch my meaning, by using creative timings and rhythms, you could spice up an otherwise "boring" or "standard" chord progression.