hi, IT guy here.. so the issue is that most internet forums can display images that are 800x600 or 1024x768 or even larger on todays larger 16:9 ratio LCD monitors, and those pic sizes are just fine to see good detail on a computer screen, but all the new phones out there have 12 megapixel cameras and save pictures large enough to print a sharp looking 24 inch by 36 inch, or even larger, printable poster, which makes the computer file something like 3000x4000 pixels and that ends up really massive on an internet forum running phpbb or vbulletin. Some forums have mods installed to auto-resize or create a smaller thumb-nail preview which you can click to then open the full-size pics, but some default installs or phpbb arent as heavily modded (3rd party mods written by random developers can be a security problem if not vetted carefully forum admins) so uploading a pic from your phone is passed along in a post at full-size and then people have to scroll around to see the full pic and the forum software does it's best to display the other forum boxes as best as possible.
If you connect your iphone via USB and copy pics to your computer, you can use free software such as Paint.NET, which is a free alternative to something like Adobe Photoshop, and you can open each pic, crop them, and resize them to 1024x768 or smaller and Save As to a new name, then when you upload as an attachment here it actually looks good and isn't over 2MB. If you prefer something easier than Photoshop or Paint.NET image editors, as someone mentioned, you can upload very easily to imgur.com and then click a big Edit button, and easily crop and resize and save the pics, then in imgur find the direct link for use on forums and you'll see a link that has the [img] commands already in the link, simply copy it and paste that link here on the forum to display inline images that are hosted at imgur and display nicely without having to upload them here as an attachment.
Hope this helps,