Image via Wikipedia
Most users run to first to check their Flash capability, and they are told that Flash isn't working for them. YouTube helpfully offers a download from the Adobe site, but this doesn't help many new users.
Solution #1: Ask Adobe for help
Ask Adobe to place an apt:adobe-flashplugin link on the download page that YouTube links to. Make sure that this link is clearly for Ubuntu users.
The user will click the link and Flash will be installed from the repositories.
Solution #2: Re-write the YouTube link to be an apt: link.
We could use Greasemonkey and a userscript to rewrite the link to Adobe into an apt: link installing the software. This would require Greasemonkey to be installed by default. There could be space and security ramifications.