PIN msgs are through BIS (data) if you cancel your plan, you will ony have TXT msgs everyhing else will be non functional... basically pointless.
If you had a Treo or another PDA device besides a BB then cancelling your data package would not be as bad, since they would still act as a PDA until you got into wifi range, and you would still have all the features.
Verizon Blackberrys i believe are the only ones without WIFI.... if you have another carrier with wifi, id save the extra money and cancel the data package.
i3-2100, 8GB, 90GB Vertex3, 1.5TB HDD, HD6850OC, 23"ACER LED Monitor (Gaming Rig)
1.83ghz Macbook 1,1 (School work, Websurfer)
4GB Mini, 2GB Nano, 30GB Video, 8GB iPhone 3GS, iPad1
BB Bold 9900