U have to DL. I don't think there is an AIM for Verizon though. There is an AIM for BB but I don't know that VZW has that support. At least I haven't found it yet.
There are third party apps you can download to get aim. If you search you can find out what they are but off the top of my head jivetalk is good from what I hear.
Posted from my CrackBerry at wapforums.crackberry.com
You are on Sprint/Nextel. The OP is on Verizon. Aim does not come
as a preloaded app with every carrier and in some cases can't be
used at all because the carrier does not make the Service Book
available for it.
there is a program via Verizonwireless called MobileIM. It allows you to use AIM/MSN/Yahoo. I believe every msg uses a TXT. not a problem if you have unlimited TXT plan. You can direct your BB browswer to VZStart page and click the link for the OTA install. This is the only free option that I know for Verizon BB's. Hope this helps.
verizon does have aim i just browsed to mobile.blackberry.com and found it on there site and downloaded it. it uses data i belive but gives you a full buddy list and works great