In the age of rising and falling dotcoms, not sure how you determine a particular services is "safe" unless it is backed by a particularly large concern...and even then services come and go and EULA's change on a regular basis. You missed it, but there's a similiar discussion going on in the flytying group. The gotcha is for how long should one expects these 'free' services to last. Probably unreasonable to expect these types of services to last forever.