Affiliate Program Payout Is Too High
Here's the thing...$100 is an okay payout if you were on a network like CJ, Linkshare, and Shareale. Because affiliates have lots of choices so it's easier to make that threshold.
Hootsuite is a very niche program and to have $100 payout is ridiculous. If your price point was higher then you might have a case. Furthermore you have to search and search to find out how much you get for each signup so this leads me to believe that you don't want affiliates- you just want people promoting you for free. Either that, or you have an experienced person managing this program.
Either way, your payout needs to be lower- $25. That's motivating enough for affiliates, but it's not too low to create to much paperwork.