Sometimes people don’t know what is good for them.
Here’s an example:
You cannot replace the battery in the iPhone. Because of this Apple have been able to make the iPhone much lighter and thinner than it would be if the design needed to incorporate a removable battery cover and place the battery in a position where it could be easily removed. As Steven Johnson points out, Apple are betting that a smaller phone with fewer moving parts is worth the trade off.
You cannot use HTML formatting when describing stuff you are selling on Trade Me. Everybody wants their listing to stand out, so this is commonly requested. However, when everybody can make their listing stand out no one actually stands out – it’s just an arms race. Trade Me prefers a consistent layout where information always appears in the same location. The alternative is eBay, where every listing looks different and typically looks like a bomb just went off with different fonts, multi-coloured text and animated graphics everywhere.
Can you think of others?