A couple of times I searched for an efficient way to monitor the UBC failcounts of OpenVZ containers on a hardware node with Zabbix. Most solutions I found on the net were about using items for each UBC and container and watch for changes in the failcounts. But I never liked those many items, each item needs to read /proc/user_beancounters, process it and send the value back to the Zabbix server.
Some time ago I tried to get the current balance of my prepaid mobile phone plan in order to implement some kind of notification if it is lower than 10 Euro. Unfortunately my ISP doesn't offer any API to get this information automatically, so my first attempt was to send a POST request using cURL to login to the website of my ISP and then parse the HTML to gain the current balance.
I recently sort of locked my workstation while I tried to query a SOAP webservice at work about for 24000 entities. While my request was as simple as "list all entities you know" to the server, its response was heavy, obviously.