I've been using predictive text (T9) on my mobiles for years now - that's how people can hammer out a text message in a few seconds without looking.

Hand-writing "telephone" on paper is a lot slower than pressing 835374663; indeed, T9 is probably as quick as a QWERTY keyboard. It's quite efficient, too - each thumb moves a maximum of ~10mm; usually only ~3mm.

Compared to leaving an answer phone message, there's no contest - dialling the number, waiting for connection, listening to the voicemail introduction, recording the message, and hanging up vs. 10-15 seconds to tap it out and hit send.

The mobile phone keyboard, with T9, is actually a damned good interface - I miss it when I use touchscreen PDAs with handwriting recognition. Predictive text is better than Graffiti, and better than thumbboards. What's not to like?