SugarSync has gotten good buzz from reviewers who have tried it and reported about their experiences in blogs and articles. Despite that, I think I only personally know of only a few people who use it. SugarSync is a over-the-air network backup service for desktop and mobile devices. It works with Windows, Mac OS X, the iPhone and now Android phones...

SugarSync extends backup/sync/share service to Android, eyes netbook market (Venturebeat)

They seem to be slightly pricey to me ranging from $50 per year for 30GB storage to $250 per year for 250GB storage. My comparisons are Microsoft's Skydrive which is free for up to 25GB storage and Carbonite which costs $55 per year for unlimited backup. However, neither of those services provide mobile device service.

SugarSync has two issues to deal with from what I can see:

1. If Android support was a play towards Android netbooks, they are not going to see much, if any, revenue from it until 2010 now that Acer has delayed their Android netbook launch.
2. If Google ever releases the rumored Google Drive service, a lot of cloud storage services are going to need to reposition their service plans.