I'm glad you posted an actual size. I'm always curious what others feel is a large database, to me, 150G isn't overly large at all. The company I work for processes phone records, where we receive about 6M new records each day. Depending on the database (some for KPI metrics, some for warehousing duties, etc.) the sizes vary dramatically, but our "monthly" databases are typically in the 250G range, while our largest is currently just under 3TB. I checked what I believe is our largest table, and it currently has just under a billion records. It's been higher in the past, but we've lowered the # of months of data stored there recently.
We are a Microsoft shop, and all of this is in SQL Server. For normal storage/queries, a decent SQL box will suffice depending on how many users are hitting it, etc., but we built a custom distributed processing system to do the actually processing work.