Teaching face-to-face or always requires engagement first. Engagement leads to better attention, and retention. Fun is a major way to engage. So...
Thanks to folks like Clark Quinn games are receiving more mainstream acceptance and adoption in eLearning circles. More developers are looking to offer instruction through games. Games provide intrinsic motivation, peer recognition, opportunities to explore, individual accountability and choice.
I recently experimented with FourSquare. At face value you check-in to allow friends to know where you are. The value proposition for 4SQ is to mine the demographic goldmine by knowing where and how often people go places and allow them to be marketed to accordingly. Why do it? For the Points!! and the Badges. the recognition provides the motivation to keep one engaged and continuously checking in. Game mechanics like additional points for being a mayor rewards repeat behaviours. Competition with friends ensues...
Most recently Google+ launched and was adopted quickly. The supposed killer feature is to group friends and share information by those groups or circles. Other services have offered this but the g+ way of dragging and dropping is game-like being more fun which means people are more likely to do it.
My favourite anecdote on fun would be the Khan Academy. This story by Wired tells it best. One mans passion to teach is fundamentally changing traditional education paradigms of lecture and homework. His videos are casual in nature, he speaks simply without speaking down to the viewer. Practice problems track the number of correct answers in a row, badges and stats are visible to motivate and show off.
Games can provide a great template for improving the fun-factor and engagement of our eLearning. The skill will be to ensure as designers we don't go too far down the game spectrum and lose the instructional objectives.