I agree that some sort of persistent voicemail indicator (message waiting lamp, MWL) needs to be implemented and that Benny is correct in his belief that this is not a request appropriate for brainstorm, for the very same reasons he mentions.

Contrary to what other posters indicated, in the US at least, this seems to be a standard expected feature. I've used phones from half a dozen vendors on every major carrier in the US over the past several years and every single one has had it. A quick informal survey around my office indicates that everyone here expects a persistent MWL, and perhaps most importantly, this feature exists on the Motorola Droid, which is arguably the comparable competitor to the N900 in this market.