Building upon standards at least increases a chance that the critical mass of users will be reached sooner, because people completely unrelated to maemo will participate.

There is, for example, XEP-0080: User Location. It can provide GPS-like information like lat/lon, but also less exact string values like the country or city you're in (or both, of course *g*).

As with many exciting XMPP-extensions, it's not really used today (I'm not aware of any client that makes use of it, at least), but still it would be better to use XEP-0080 than re-invent the wheel.

Nokia Chat (S60), for example, is XMPP-based. Some Jabber desktop clients at least have XEP-0080-support on the roadmap.
Now imagine what would happen if Nokia Chat/S60 would add XEP-0080 and XMPP in the tablet's Telepathy-framework would, too:

Via Telepathy, location support would be part of Gnome 2.24 and enter the desktop more or less automatically. Probably developers of other clients wouldn't want to fall behind and put it higher on their lists. That's how you reach a critical mass. But what does Nokia do? They add location features to their S60-Chat-Service, but do not use the standards, so nobody outside the small group of S60-Chat-users will ever be able to use it. And I bet if they ever integrate location awareness into the tablet's IM, it will be non-standard and incompatible even to their in-house-development for S60 phones.

EDIT: After writing this, I found some infos from mailing lists that suggest that at least the telepathy developers think of integrating XEP-0080, based on geoclue information. This could mean that Gnome and the tablets can share location information. - If the usual Nokia madness makes them deliberately exclude S60 phones from this network, they should seriously consider going out of business.