Happens all the time to every team. Go back through the drafts, and about 7 players a year never make it to a single NBA game. That's like 15%. A bunch more don't make it more than a season or two. About half the players in the league don't make it past four year, and certainly many players bounce around the fringes of the NBA, providing little value for their original team.
Let's look at Colton Iverson's draft, from 40 on down:
40 - Grant Jerrett -- signed a deal the at the end of the 2013-2014 season so OKC didn't have to pay the luxury tax. Played a total of 25 minutes for them the following season, before being sent to the Jazz as salary filler in the Kanter deal. He played 26 minutes for the Jazz, and then was released that summer. Now he's Portland's version of John Holland.
41 - Jamal Franklin - He averaged under 8 minutes over 21 games for Memphis in his only season with the team. Has spent time in China, the D-league, and a week with Denver since that time in Memphis.
42 - Pierre Jackson - Was New Orleans version of Abdel Nader after being drafted. Tore up the D-league (set scoring records), went overseas mid-season, was traded to Philly in the offseason, when he tore his Achilles in summer league and has still never appeared in an NBA game.
43 - Ricky Ledo -- played 44 minutes over 1.5 seasons for the Mavs before they waived him. Got a lot of minutes at the end of a season for a terrible Knicks team, and spent last year in the D-league and Puerto Rico. Now in Turkey.
44 - Mike Muscala -- as far as this list goes, Muscala has been very successful. That success had meant he's the fourth big in Atlanta. Mike Muscala is who I hoped Colton Iverson would be for us. Of course, that equates to under 1300 minutes in 3 NBA seasons.
45 - Marko Todorovic -- 24 years old, still in Europe. He has two years left on his contract with his Russian team, which he signed with last season.
46 - Erick Green - spent his first season after being drafted in Europe. Then spent a season as a not good player on the end of a bad Denver team's bench. Was released a week into last season. Spent his time in the D-league, a 10-day contract with the Jazz, and is back in Europe.
47 - Raul Neto - 2 years overseas after being drafted before making it to Utah last season. He was the starting PG last season after Exum got hurt. Exum is back and George Hill is on the team, so it'd be surprising if Neto got anywhere near the same amount of playing time as last season.
48 - Ryan Kelly - Got consistent minutes for 3 of the worst Laker teams in franchise history. Currently looking for work.
49 - Erik Murphy - Played garbage time minutes for the Bulls in his rookie year, before being cut in a move to avoid the luxury tax. Picked up by Utah, for while he never played, then sent to Cavs and then the Celtics as the Cabs tried to create a cap exception. Cut by us, and is in Europe.
50 - James Ennis - Spent a year in Australia, then a year in Miami's rotation. Was sent to Memphis the following season, who sent him primarily to the D-league before releasing him. Caught on with New Orleans at the end of last season because he could walk, unlike most of their team, and is now back in Memphis.
51 - Romero Osby -- didn't make it out of training camp with Orlando, and wound up playing in Maine, then Europe, then Maine, then Puerto Rico, and now Israel.
52 - Lorenzo Brown -- didn't make it out of his rookie camp with Minny. Has bounced around the D-league and various NBA teams on 10-day and rest of season contracts.
53 - Colton Iverson - why I'm writing this post
54 - Arsalan Kazemi -- spent two seasons overseas before Philly renounced him. He was the first Iranian player drafted however, so that's neat.
55 - Joffrey Lauvergne -- spent 1.5 seasons overseas after being drafted. Now in the Nuggets rotation, so he's definitely been a successful pick.
56 - Peyton Siva - spent a season bouncing between Detroit and the D-league. Was released the next summer, spent a year in the D-league, and is now overseas.
57 - Alex Oriakhi -- looking at his fourth year not in the NBA. Kings got his rights from Phoenix in the IT sign-and-trade. So that's interesting.
58 - Deshaun Thomas - Spent 2 years in Europe, then was a training camp cut by the Spurs. Spent last year in the D-league, now in Turkey.
59 - Bojan Dublevix - Remained in Europe. Doesn't seem to be coming to the US any time soon.
60 - Janis Timma - See above.
It's really great when every draftee works out, but as the above list shows, it's unlikely any given player picked in the back part of the second round will work out.