[mixedbit]

My guess is that the reason they are closing this is the cost of bandwidth. Dropbox allowed to host publicly all types of large files and exchange such files by a link that did not require any interaction with DropBox to download. It seems really hard to monetize such usage.

[bane]

I believe they already do some kind of bandwidth monitoring, so I could also see them just passing that along to subscribers who use too much. I would have also hoped their bandwidth costs would have improved when they moved to their own cloud instead of S3.

[TeMPOraL]

I vaguely remember that they were able to throttle/block off a public file when it caused unusually high traffic.

[RachelF]

Perhaps, but the MPAA/RIAA and what happened to KimDotCom are also probably a big factor.