Honestly, there is now way on earth I'd allow my company to use Slack given their Termination clause. It's a nice idea, but total loss of control of your data is just not worth it.
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We also reserve the right to terminate your account (or the access privileges of any end user) and this TOS at any time for any reason, or no reason, with or without notice. Upon termination of your account, we will have no obligation to maintain or provide Your Data, and will delete or destroy all copies of Your Data in our possession or control, in a reasonably expedient way, unless legally prohibited.
</snip>
<snip> We also reserve the right to terminate your account (or the access privileges of any end user) and this TOS at any time for any reason, or no reason, with or without notice. Upon termination of your account, we will have no obligation to maintain or provide Your Data, and will delete or destroy all copies of Your Data in our possession or control, in a reasonably expedient way, unless legally prohibited. </snip>