I don't believe that. I don't use any of the Sense stuff and I've run out of memory. It started when I downloaded big PDF email attachments using K9.
The Incredible is NOT the only powerful Android phone out there. There are tons of them now, Droid X, Samsung Galaxy S (Fascinate, etc.), Nexus One, Nexus S, EVO, on and on.
I haven't see this problem reported on other phones.
Googling anything about /data/data or 150MB limits on Android yields nothing.
This sounds like an HTC and Incredible unique problem.
150MB is simply a joke when the phone has 6GB, as in 6,000MB available not counting another 8,000MB on the SD card.
Most iPhone games use tons of space. Apps and their data on iPhones use data measured in gigabytes, not 150MB (in total, not individually).