Most of my income comes from layout work and so the below is really from that perspective. It is a must that I retain the font versions used in the production of said work. (A new version can cause reflow, line spacing issues, etc.)
Even if I was still doing web-work, I wouldn't want my fonts swapped out upon a new version being available & served up.
I personally would not purchase fonts from a distributor who had their hooks into me & my computers and/or servers that deeply.
If I had to pick a major player's site, it would be MyFonts. Though I don't like that they changed the site to always default to showing image tiles, it is the easiest to browse, navigate and purchase from for me.
That said, I prefer simpler sites. I don't need fully interactive sites. I don't need a slider to show me a half dozen tiles.