I recently chatted online with representatives of the Wi-Fi Alliance, the WiMAX Forum and the GSM Association in an effort to understand how enterprises will apply emerging mobile broadband services going forward. With a quarter-million Wi-Fi hot spots worldwide, it's my take that Wi-Fi could become the default, pseudo "mobile WAN" of choice for the masses of traveling executives. Obviously, Wi-Fi won't cut it for field service workers or those out in the desert or on an oil rig. But for mainstream use, why choose a mobile data plan with its high data usage and roaming charges?

In the context of these questions posed to the text-conference attendees, below are a few key nuggets for technology and service comparison that I took away from the conversation. To read the complete transcript of our discussion, click here.

* Footprint

Wi-Fi: 250,000 hot spots worldwide. The number of hot spots with Draft 802.11n is unknown, but “is happening already as operators upgrade their technology every 18 to 36 months,” according to Edgar Figueroa, executive director of the Wi-Fi Alliance.

Mobile WiMAX: Currently deployed by about 70 operators worldwide.

LTE: To be commercially available “in some markets” starting in 2010, “of which we expect North America to be one,” said Dan Warren, the GSM Association’s CTO.

HSPA: 200 live networks in 114 countries with 60 million worldwide subscribers.

* Per-subscriber bandwidth

Wi-Fi: Aggregate 150Mbps up and 150Mbps down in 802.11n networks, shared by “n” number of users in a given hot spot. Note, though, that most hot spots use 802.11g technology, offering 54Mbps shared, for a real-world shared throughput of about 25Mbps. Per-user bandwidth depends on how many users are sharing the RF resources at one time.

Mobile WiMAX: About 2Mbps

LTE: Tens of megabits per second per user

HSPA: 1Mbps downlink average but some markets offer 3.6Mbps, 7.2Mbps and 14.4Mbps services. Uplink speeds: to be determined.

As a side note, I found it interesting that, mere days after our chat, mobile WAN titan AT&T announced that it would acquire Wayport’s Wi-Fi hot spot business, adding 20,000 hot spots to its U.S. footprint and 80,000 globally. Perhaps this is AT&T’s answer to getting around these steep global mobile data usage and roaming charges that it has to pass along to its customers.

Joanie Wexler is an independent networking technology writer/editor in Silicon Valley.