• Tight space constraints make rewriting much harder, potentially dissuading contributors from moving ThreadMode to DocumentMode
• Harder to refactor DocumentMode, as the actual text being refactored is split across two Web pages.
• Pages will be too large for those with small monitors, who browse in narrow windows, or who browse with large fonts (e.g. the visually impaired)
• Pages will be very small for those with large monitors, or those who browse with small fonts.

(from SlideWiki)