A common hazard is taking too long a view, plan too far ahead and show no intermediate results to the end users. The result is a project that gradually looses credibility and support. The end users generally react negatively when (finally) results are shown to them. In a worst case scenario the goals to be achieved may have changed over time, rendering the project results partly or totally useless.
Stick to incremental result delivery with a max event horizon of 4 to 6 months!