Hi Jason,
you might want to consider adding "Lead Source Details" custom field that would be specific to a campaign, then limit the number of values used as lead sources (webinar, tradeshow, website, referral etc).
So if the "Lead Source" is "Webinar", "Lead Source Details" is the name of the attended webinar.
If the "Lead Source" is "Website", the "Lead Source Details" is the name of the downloaded collateral.
This way the lead source is normalized which makes it more scalable and easier to use in reports.
Cheers,
Elena.