This eMarketer article reports on a survey of 1,115 US Internet users as to how they feel about pre-roll ads in videos.

Results:

• 52% said they would skip a pre-roll ad if one were presented.
• 20% said they would close the video altogether if a pre-roll ad were presented.
• Others said they would do something else until the ad ended, or mute the ad.

In another survey done in the USA, UK, Australia and Canada, respondents aged 18 to 69 were asked for reasons they abandon digital videos.

Results:

The number one reason for abandoning a video was "playback of poor quality", cited by 65.8% of respondents.

Regarding ads:

• 61.8% said they'd abandon a video having too many ads within it.
• 26.7% said they'd abandon a video if presented with a pre-roll ad they couldn't skip.
• 16.4% said they'd abandon a video if presented with a pre-roll ad, skippable or not.

So, from both sets of results, if the numbers from the samples are applicable to the general online user population, somewhere between 43% and 72% of Internet users will never see a pre-roll ad. And between 20% and 43% will never watch a video preceded by a pre-roll ad. Those are serious numbers suggesting that a little more subtlety is called for when using videos for marketing.