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If you don't have a texting plan and someone sends you a text, it costs you money. Unless you know to have your carrier disable it on your account. iMessage doesn't necessarily cost you anything, except for tiny bits of data. Chances are this isn't going to be enough to put anyone over their data usage.

But even so, you can turn it off. Just like you could turn off texting. It's really not any different. If you don't know to turn it off, it could cost you money. If you're worried about your friends sending you video, tell them not to. I can do that just as easily as I used to tell people not to send me a text unless it was an emergency because I would get charged for it (back when I didn't have a texting plan at all).

iMessage has the ability to save people money. Many won't need an unlimited texting plan anymore. And if it was turned off by default, everyone here in the forums would be screaming that it didn't work, etc. etc.

Well said. Count me a one of those that iMessage saves money. I pay $5 for 200 text messages on AT&T and I regularly now exceed that amount. The only other text message plan available to me is unlimited for $20/mo but as a significant number of my messages are sent to other iPhone users, I now no longer need to upgrade, thus saving me $15.

And while I don't know the specific amount of data used by an iMessage, I can't imagine it's very much and doubt these messages significantly contribute to your data usage, unless you're sending thousands of messages. I understand the OP's MMS group message scenario but really, how often of you need to send these messages? In these cases, shut off iMessage and use your allotted text plan. Also, aren't photos sent via iMessage or SMS significantly compressed to reduce file size?
 
It's not that you'd need 10,000 cores to run it. They need mega processing power due to millions of people hitting it. An individual phone wouldn't need that much, but you'd likely need more processing power than is available on the iPhone 4S presently and you'd need a lot of data storage. They use advanced algorithms and run these against a large speech corpus, most likely. I'm not sure of the size of their corpus, but it'd take up a large percentage of the iPhone's memory or it would max it out completely. And how would you update it? You'd have to update millions of iPhones and the updates could be quite large. Being server based, it's much easier to update and tweak on a daily basis (or even more frequently). It probably keeps their algorithms more secure, also.

As for it not running on anything other than the 4S, I think that's just a marketing decision.

Completely agree :)

As for iMessage, I think it's genius. I love it. I also have unlimited data and unlimited text (grandfathered AT&T), so I don't worry about limits :)

But I do agree - Most people don't know they have it on

E.G. Questions from people I know - "Why do sometimes I have blue bubbles for text messages and sometimes green?"
 
Completely agree :)

As for iMessage, I think it's genius. I love it. I also have unlimited data and unlimited text (grandfathered AT&T), so I don't worry about limits :)

But I do agree - Most people don't know they have it on

E.G. Questions from people I know - "Why do sometimes I have blue bubbles for text messages and sometimes green?"

I got asked that question by quite a few people who were trying out my phone. Funny thing is, they have an iPhone 4 with iOS 5. I said it is to distinguish regular texts from iMessage texts. They said they saw iMessage on their phone, but didn't know what it was so they have it turned off. Now that I look through my contacts, all but 2 have iMessage disabled.

People just don't understand what it does, so they turn it off. Or like you said, have no idea its even turned on.
 
Wirelessly posted (Mozilla/5.0 (iPhone; CPU iPhone OS 5_0 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A334 Safari/7534.48.3)

On the data use of iMessage.

Kik is a similar 3rd party texting service (available in the AppStore) that has similar features.

This quote is from Kik's support site:

7. Does this use SMS or data to send and receive messages?
Kik Messengers uses your data plan or WiFi to send and receive messages. Less than 1KB of data is used to send messages on Kik and it uses approximately 100KB to send or receive a picture.


So if we assume that Apple's iMessage uses similar amounts of data:


With a 2GB data limit:
-You could send/receive 2,097,152 texts.

-You could send/receive 20,197 picture messages.

Even if IMessage uses ten times more data than a Kik message, your looking at over two-hundred thousand text iMessages or two thousand iMessages that have pictures.

My friend, iOS 5 isn't perfect. I have a few gripes.

Data usage with iMessage isn't one of them.

Source link for quoted portion: http://m.kik.com/support.php#Q7
 
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