Digital released songs

Perhaps, this may have come up for discussion in the past. As an extension of the "iTunes Finds" thread, just wondering with a number of tracks being released digitally and not on a physical CD, are those considered for inclusion in the database?

Thanks for all the hard work, Pat. The database is an invaluable resource.

Any database of "hit songs" that includes music from the last 15 +/- years needs to encompass airplay only tracks since a significant number of "hit" songs were never commercially released as singles.
This brings up the question though...what is a "hit" song in the 21st century? A song that gets lots of radio play? In the old days that would have been referred to as a "turntable hit", ie-one that for whatever reason got played a lot on the radio, but only generated weak sales. Reasons for these songs' existence vary, from a need to balance a playlist to payola. In retrospect, were they legitimate hits or not?
I realize today that most any song is available as an individual download, and I'd imagine these are counted by the trades (or at least ones downloaded from the major download sites, ie-Itunes & Amazon).