If my opponent has a dead Ikoma Yasuko experienced in the discard pile:
Lion Clan • Courtier • Experienced Shosuro Yasuko • Unique
Battle: Even if Yasuko is home: Target a Personality not at the current battlefield. Move him there. If you do not control him, straighten him.
Political Reaction: Before another Lion Clan Personality is destroyed, destroy Yasuko: Negate the Personality's destruction.
When he tries to copy the ability from Yasuko experienced onto another personality, can I react with Share the Blame?
Hall of Ancestors
Dead Personalities you own can not be removed from the game.
Battle/Open: One of your target Personalities copies an ability or keyword from a target dead Lion Clan Personality you own (until the turn ends).
Share the Blame
Political Reaction: After another player targets a Courtier with an action, dishonor one of your Courtiers: Dishonor the Courtier the other player targeted. You, then the other player, each lose 3 Honor.
ANSWERs: Yes. The Courtier was targeted.
http://rules.l5r.com/Glossary_X-Z: "When “your” and other possessive forms such as “the player’s” or “his” refer to a card, this means “controlled by that player" if the card is in play, or "owned by that player" if the card is not in play."
Yes, when a Hall of the Ancestors player targets his dead Ikoma Yasuko, you have a valid trigger for playing Share the Blame and can do so as long as you have one of your own Coutiers to pay the cost.
Please note, though, Share the Blame will not dishonor the dead Yasuko, as I found ruled
here, via the Search feature (I'm truly happy to help, but your continued aversion to said feature does perplex).