I can give you rough idea in explanation as I started working my first job right before minimum wage decided to go up. When I was 16 I got a job at 4.25/hr. Candy bars (just a given item of small value to show the increase that took place - not to mention something I bought alot of back then) costed $0.33-$0.49. Then the idea of taking minimum wage to 4.75 came out. Of course, naturally, I was all about this as it meant more money in my pocket or so I thought. (months later it raised to the 5.15 it is now)
However, my family explained how this was a bad move. Here is why. The grocery store I worked at had alot of minimum wage employees as do many many companies out there. SO naturally to make up for this hit on their profits for payroll, they had to increase prices to compensate. Not only for the loss of money but to adjust to the new economy as well. There is more money out there for grabs so campanies not only raise prices so that they can pay their employees but add in a bonus profit cost to take their fair share of the bigger pie.
So when your getting a minimum wage raise, you have to realize prices are about to go up. That same candy bar is now $0.79-$0.99. The price doubled, but minimum wage didn't. Before the candy bar was worth about 4 mins. of work. Now it costs about 10 mins. of work. That is an expensive candy bar. Minimum wage people are actually now more poor than they were before minimum wage went up.
Also, the people that have jobs that are paid more than minimum wage can't get as much from their paycheck anymore. This $0.90 raise in minimum wage has demoted some workers in the workforce. How would you feel if you had worked 2 years to get up to $5.50/hour from $4.25 and now minimum wage goes up. 2 years of work are now worth less than when you started the job.
Raising minimum wage is targeted at, ideally, decreasing income disparity. But decreasing income disparity (I personally think) is better handled by bringing jobs into the economy that have competative wages and not rely on what the minimum standard is. Here in KC your not going to make it if you work a full-time minimum wage job. Even if you got an extra 10-20 hours of overtime that week. Heck, take 40 hours of overtime everyweek and you would be lucky to get by for a year or two.
Minimum wage being raised seems like an obvious solution, more dollar bills are printed out to accomodate it, thus decreasing their value. A 1994-95 US dollar was worth more than a 2006 by a very noticable amount... if your broke. If your rich, you probably didn't notice too much. Middle class, I am not sure how much it affected them.
There has to be at least 1 benefit to this though I would think. I have never heard a valid one to this day though.
EDIT: I will throw in that the candy bar is a bit high upon thinking about it because it is a cheap item. Something that costed about 20 bucks would now be about 25-30. So just under 5 hours of work to buy it in the 90s and between 5-6 hours now. The higher priced the item, the less the difference. The amount of high price items you can afford at minimum wage, not much.