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There is nothing wrong with most hay brought in from out of state!  It is important to know your source.  When we import hay to save a few bucks we also run a risk of introducing some problems.  You should be able to get out of state hay cheaper because your up front cost to investigate the source is obviously much higher and even then you are taking on added health risks to your horses.  Yes, that means visiting the farm and seeing first hand to evaluate- qulaity of operation/production; quality of storage; pulling your own nutritional analysis; testing hay for moisture.  Of course you need to know what you are looking for and have the proper equipment  (moisture probe, core sampler).

Things to be careful of:

SEED PRODUCTION FARMS-  Hay that is taken at full maturity AFTER seed has been harvested.  If the hay is 1st cutting you should see plenty of seed heads.  Nutritional analysis will show much lower protein and RFV (relative feed value).  The risks here is not so much a heath risk but nutritional problem- this hay will need much higher supplement inputs to keep your horses in condition... in other words you need to estimate your TOTAL FEED COST when you buy this lower  quality (cheap) hay. 

EPM  (Equine Protozoal Myeloencephalitis) POTENTIAL-  This is rare in Colorado because the primary culprit isn't seen here.  BUT it is seen in our NEIGHBORING STATES TO THE EAST.  More cases show up in Colorado in drought years as a result of increased out of state hay.

http://www.extension.org/pages/Opossums

about EPM see:  http://www.aprendelo.com.br/rec/equine-protozoal-myeloencephalitis.html

also see:  "Equine protozoal myeloencephalitis (EPM) is a serious and often fatal neurologic disease of horses, but few studies have investigated risk factors."      "CONCLUSIONS AND CLINICAL IMPORTANCE: Because the risk of EPM occurrence on operations is closely tied to factors that impact exposure to opossums, their feces, and their environment, controlling these exposures may be important in preventing the occurrence of EPM"  . http://www.ncbi.nlm.nih.gov/pubmed/18466255

also see: 
Prevention of EPM
Strategy Favorable Result
Secure horse feed and water sources Limits fecal contamination by opossums
Limit wildlife access to garbage and feed Makes the area less attractive to scavenging opossums
Install wire mesh on stalls Limits access of scavenging opossums to horses, stalls
Confine horses in protected stall at night Provides controlled area preventing opossum access to areas where horse is eating and drinking
Close stall and barn doors even when horses are not present in the barn Prevents opossum access to stabling areas where horses eat and drink
Limit stressors:

• Arrange comfortable herd dynamics and social interactions when possible
• Manage horses' nutrition wisely
• Implement strategies to alleviate transport stress
• Devise reasonable competition and training schedules and performance expectations
• Facilitate good foaling environment/situation for pregnant mares
• Implement preventive medicine programs to ensure good health--deworming, routine immunizations, dental care, and farrier care Allows optimal function of immune system
Minimize barn contamination:

• Steam clean the barn
• Use clean boots or boot covers Minimizes cross-contamination in barn areas where horses congregate
Work with your veterinarian to evaluate neurologic or musculoskeletal concerns Ensures early testing, diagnosis, and appropriate treatment when necessary
Research is still in process for a vaccine that works Vaccine against EPM is a future possibility
Prophylactic use of antiprotozoal drugs might be a future possibility More research must be done to substantiate safety and efficacy and to obtain FDA approval for these drugs http://www.thehorse.com/ViewArticle.aspx?ID=8414

ALFALFA BLISTER BEETLES- 

"Alfalfa hay from Kansas, New Mexico and Oklahoma, in particular, is more often associated with incidence of blister beetle poisoning.  This is due to the toxicity of blister beetles from these states and the large amount of alfalfa hay produced and shipped from these states.   In addition, midsummer alfalfa is more likely to contain dead blister beetles than first-cutting hay or late cuttings as the adult beetles are only active during the summer months.  Early May and late September are the best harvest dates for buying alfalfa hay for horses.  The process of mowing and crimping at the same time during harvest crushes and traps the beetles in the hay.  Farms that use separate mowing and crimping procedures, or that use no crimping process are not likely to have a problem with blister beetle contamination. "

http://128.121.9.111/articles/health/102706_blisterbeetles.jsp