just dont go too crazy with it and you should be fine... i have been tethering with several different methods for 2+ years now and have never gotten in any trouble from verizon...
but if your data usage jumps from 1gb to 100gb in one month, it might raise a flag with them.
There is a FoxFi plugin that enables/adds a proxy method to proxy your connections through the browser so it helps keeps things under the radar even more (since carriers use many different methods to detect if you are tethering or not)
i been using this app since the day it came out for my old stratosphere and it worked just fine (and i download 10-20gigs a months no torrents just PSN games and Steam games i buy)
verizon doesnt know if you are tethering or not. it is data either way. in this case, the data looks like it is coming from that application. they would have to go looking for that to find out if you were tethering or not. I have been tethering without a tethering plan for years. no grief. not a word.