1987: http://en.wikipedia.org/wiki/File:Macintosh_SE_b.jpg 1995: http://en.wikipedia.org/wiki/File:Zip-100a-transparent.png 2002: http://reviews.cnet.com/pc-card/kodak-20-mb-compactflash/170... (Note the Discontinued tag)
Ok...enough sillyness. 20MB? If you have any index on your data this is really more like 12MB of data. I'll admit that the 20MB is free and enough to get started with a design, but there no way you'd be able to run any sort MVP on that amount of space. With the current lack of logging a couple hundred visitors would fill that up in a few days with just web traffic logging. $10/month isn't that expensive for the full 10GB...actually a great price point....but the 20MB just looks silly.
If I were you all I'd up it to 1GB. 20MB just looks so...1992ish? Heck even 100MB would look more appealing.
Please don't take this as too much of criticism. I'm using the service and love is so far. I'm sure you have some spreadsheet somewhere that says the free DB should be 20MB and I'm sure that there is a very logical reason for picking the number. But it is a bad number.