No, that would kill the server, actually. First off, it's not the recommended way for Facebook as they don't want you (and every other site on the planet) hitting their servers constantly just to check if any one of your user's have updated any piece of their profile. That's why the recommend the Real Time Updates feature and if you have a massive site that were to do the cron job method, you'd likely get your account suspended for so many requests.
On the hosting side, the cron job would get very slow as new users join the site. If you wanted to poll every hour (lets say) and you have 10 users, no problem. If you have 10,000 or more users, that's 10k requests (at least) per hour in addition to the processing of that. A slow host would die.. and 10,000 users isn't uncommon even on 'slow' sites.. if they've been a while a long time.
You could always stretch the cron to 24 hours or something (or split it into pieces 10% of users every hour, etc), but that just delays the inevitable wall. The Real Time Updates simplifies it by having Facebook tell you an update has happened, and you're notified within 5 minutes of the update. So, it works out to less 'work' for the server and you get updated quicker.
Hope that makes sense, but feel free to ask more.. this is something we've done some investigation on, but there's always alternatives we could have overlooked
Alex