Upload & Sell: Off
Like I said, yeah, the idea is good, and I've considered it at my own wedding! But I found that the hardest part is in implementing them consistently and with "watchable" quality. With all the guests having WiFi/3G/4G enabled devices at one place, and especially when the venue is at a hotel/country club/restaurant/event hall/etc., bandwidth is a real issue, even if it is over WiFi.
If you're offering a free service (on top of your other paid services), and with very low expectation of streaming quality, that may be ok, but it would be a bit frustrating to watch on the other end. I just don't see grandparents/family/friends, sitting at a computer/couch watching a very jittery and unstable broadcast of a wedding. I think they'd rather have a high quality condensed video very shortly after the wedding (hosted on Vimeo or something); I know my friends and family did.
The videographer that we hired whipped up a great 5min condensed video of our wedding ceremonies (yes, plural) within hours, and we were able to point our friends to a Vimeo link the night of our wedding (considering wedding day prep started at 7:30am, our wedding ceremonies formally started at 9am, and ended around 3pm, highlights of all included in the video). It was a good video, and people enjoyed the length (or lack thereof) of the video, but still being able to see all the highlights, and on their own time. To them, it wasn't as important to see it the very second it happened (since it was a 12-15 hour time difference for them), but the ability to see it as soon as they wanted to, when they wanted to, was great. And since they were all viewing it at different times, and from a powerful hosting site (Vimeo), streaming video quality was great.