Now that I have a phone that is capable of doing usable internet I've been considering how I would use it away from wifi. I don't make many calls or send many texts, so I get by with a PAYG account with Virgin that costs me a couple of quid each month. This allows me to use up to 25MB of data for 30p each day, but the next MB after that costs £2! That seems ridiculously excessive. There's an alternative of paying £5/month for 1GB, but I'd probably only use it for a couple of days each month. Basically I'm generally by a PC at work or home or I'm driving. When I'm out with the family I'm not too bothered about checking email and microblogs, That said, there will be times when I want to use those services or upload a photo. I would expect that I could send a load of emails etc with my 25MB. It would be cheaper than sending more than 3 texts a day. I just need to checking how much data I would get through in a typical day with various apps pinging the net. I may have to disable some.
So I've been looking at options for my Android phone that will prevent me being hit with silly charges. This article suggested some free applications that look possible. I'll be trying out 3G Watchdog. I've put a question on an Android Q&A site. I like the Stack Overflow system for building up a knowledgebase.
When I'm on my home or work wifi, then I have practically unlimited data. I need that on my phone in order to download various podcasts with Google Listen. I'm probably not going to use streaming audio or Google's satnav system on the move.
Looking back I've been through using acoustic couplers (school Teletype), various modems (on Amiga and PC) then various speeds of cable modem from 512kb up to my current 20Mb. There's been a progression from simple text, through static images to HD video and decent quality streamed audio. We seem to find ways to fill the available bandwidth. There's talk of 100Mb and higher speeds coming in a few years, but are already in some countries like Korea. I'm not sure what you would use that for.