I was wondering about this the other day. Nowadays, it is possible to watch 99% of all top flight games in Europe live via a stream, because they are all broadcast live somewhere in the world by Sky, BT, BeIn, NBC, or Setanta. What we don't know is the viewing figures of the various games via streams. If it was possible to estimate the numbers watching, say, Saints playing Leicester at 3pm on Saturday via streams, it might go some way to showing whether showing that game live in the UK on TV would have had any effect on what was a sell out match. I've no idea how you would go about gathering data like that without intruding on people's privacy but it would be an interesting exercise.
I'm a self confessed stream tart these days.
It does not affect my (infrequent) attendance at Saints or (no laughing) Wimborne Town. These are governed by time and money restraints. For the first time in ages I qualified for a Man U ticket this time round, got almost to checkout on the site and just couldn't click to buy as I really couldn't justify it to myself and family.
I look for cheap (league cup early rounds then) options at Saints or get bought a ticket as birthday/xmas pressies. Some no doubt feel it shows a lack of commitment or passion for Saints but like many others I now have other priorities. The streams are so easily available now I think any impact on attendances has already happened. Current and future attendances will be affected only by the prices charged, in the Prem anyway. Local teams (yay go Wimborne Town!) are fighting a losing battle in most cases against the many alternative entertainments on offer.

