Is it technically feasible to "shun" particular bitcoin wallets?
Not really, if you start doing that then chain forks and a whole load of nasty things follow. There's no real way of blacklisting a "wallet", as by design there's no way of determining exactly the extent of the keys under control by a specific party, so for the sake of this discussion we will assume we have one blacklisted "address".  

Even if nodes reject transactions from specific addresses, miners can still include them in blocks without them even having to be broadcast. If some nodes decide to arbitrarily invalidate blocks with transactions they don't like, you've then got a forked network. Massive double spends occur on both forks by intentional and unintentional parties, and the network collapses in the sea of mistrust. 

Currently, some mining nodes (like mine) specifically refuse to include transactions in blocks that come from known betting site addresses, like SatoshiDice. I however don't reject blocks that contain the transactions, or I'd be very quickly become isolated from the network. 

You'll never get all the miners to agree with any form of blacklisting, so no, it can't technically happen.