Mobile data roaming - the practice of connecting to the internet via a cellular network while overseas - has always been a pastime best reserved for those with deep pockets and a penchant for surprises.
Keeping track of exactly how many millions of bytes of information you've sucked down onto your phone or laptop while travelling is difficult.
I've developed a very general rule of thumb that average web surfing and internet checking chews through about one megabyte of data for every minute I'm online.
If I was to spend an hour linked up to a cellular connection overseas, and was racking up the highest roaming rate charged by Vodafone and Telecom - $30 a megabyte - I'd be left with an $1800 expense on my next phone bill for the 60-minute experience.
That level of cost may sound ridiculous, but stories abound of unsuspecting data roamers returning home to find bills for several thousand dollars.
The ever increasing popularity of smartphones has made this so-called "bill-shock" problem more acute.
As phones get packed with more features, we are becoming more comfortable using a range of data-intensive applications on our handsets.
Using satellite navigation services, downloading email attachments and even updating your Facebook status through a mobile app all use up data.
Domestic data plans have become much cheaper and generally include a high enough cap on usage to ensure most people aren't being stung with huge bills for using mobile services.
But take those same usage habits with you when you travel overseas and the cost could be astronomical.
The discrepancy between local charges and roaming rates presents a dilemma for mobile network operators. While data roaming generates high-margin revenue, the associated bill-shock has been bad for customer relations.
Vodafone this week took a tentative step towards addressing the issue. From May 26 it is cutting global roaming rates for all countries except Australia from $30/MB to $10/MB.
In Australia, where its rate was previously $10/MB for customers connecting through the Vodafone network (or $30/MB for connections over competitors' networks) the company is running a three-month promotional rate of $2/MB.
The cuts are welcome, particularly the new Australian rate. While Vodafone is only promising the $2 tariff between May 26 and August 26, telco marketing tactics often involve introducing a temporary price reduction which is later extended and eventually becomes the norm.
Vodafone was yesterday trumpeting the new Australian rate as "a whopping 93 per cent reduction" on the extravagant $30/MB it is currently charging customers unfortunate enough to find themselves connected to a competitor's network when they roam across the Tasman.
But be warned, while it is a significant reduction from both the $30 rate and even from the $10/MB Vodafone has been charging to connect to the company's own Australian network, bill-shock is still a real likelihood for the unsuspecting transtasman roamer.
An hour-long surfing session at $2/MB is still likely to cost upwards of $100.
Bill-shock victims may no longer require a second mortgage to pay the phone bill when they get home but a new overdraft facility might be needed.
OFF THE METER
Staying on the subject of the cost of internet access, local online television network Ziln, which was launched last year, says it's delighted at a huge surge in viewership after TelstraClear "unmetered" access to its content.
This means TelstraClear broadband customers do not eat into their precious monthly data caps when they watch Ziln channels at www.ziln.co.nz.
New Zealand's restrictive monthly data limits have been a major factor in limiting the uptake of serious television watching online.
Ziln has an eclectic mix of mainly special interest content - from comedy channel LaughTV and Archives NZ content through to Al Jazeera and Bloomberg business news.
It says it reached 170,000 video views in one week after TelstraClear's unmetering, prompting a move to larger computer servers to handle the traffic.By Simon Hendery Email Simon